U.S. patent number 6,305,769 [Application Number 08/876,001] was granted by the patent office on 2001-10-23 for selective deposition modeling system and method.
This patent grant is currently assigned to 3D Systems, Inc.. Invention is credited to Thomas A. Almquist, Bryan J. L. Bedal, Anthony L. Caruso, Keith Denison, Richard N. Leyden, Michael S. Lockard, Christian M. Merot, John S. Stockwell, Jeffrey S. Thayer.
United States Patent |
6,305,769 |
Thayer , et al. |
October 23, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Selective deposition modeling system and method
Abstract
A system and associated method for forming three-dimensional
objects under computer control and from a material which may be
rendered flowable and then dispensed on a layer-by-layer basis. The
layers of the material solidify or otherwise physically transform
upon being dispensed thereby forming successive cross-sections. The
dispensing process is repeated whereby successive layers adhere to
each other thereby forming the object.
Inventors: |
Thayer; Jeffrey S. (Nahant,
MA), Almquist; Thomas A. (San Gabriel, CA), Merot;
Christian M. (Saugus, CA), Bedal; Bryan J. L. (Palmdale,
CA), Leyden; Richard N. (Topanga Canyon, CA), Denison;
Keith (Valencia, CA), Stockwell; John S. (Sylmar,
CA), Caruso; Anthony L. (Northridge, CA), Lockard;
Michael S. (Valencia, CA) |
Assignee: |
3D Systems, Inc. (Valencia,
CA)
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Family
ID: |
24130220 |
Appl.
No.: |
08/876,001 |
Filed: |
June 13, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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534477 |
Sep 27, 1995 |
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Current U.S.
Class: |
347/1 |
Current CPC
Class: |
B29C
64/40 (20170801); B29C 64/112 (20170801); B29C
64/188 (20170801); B33Y 40/00 (20141201); B33Y
10/00 (20141201); B33Y 30/00 (20141201) |
Current International
Class: |
B29C
67/00 (20060101); B41J 002/01 () |
Field of
Search: |
;347/1,37 ;364/468.26
;156/58 ;427/466 ;264/308,401 |
References Cited
[Referenced By]
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322257 |
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426363 |
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581445 |
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5-11751 |
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3-236940 |
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WO 89/02575 |
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WO |
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Other References
Hawlkeys Condensed Chemical Dictionary, Richard J. Lewis, Sr., pp.
1173-1174, 1997.* .
Wohlers, T., Cadence, Plastic Models in Minutes, p. 101-104 (Jul.
1990), US. .
Production, No-Mess Modeling in Minutes, p. 16 (Aug. 1990), US.
.
Herbert, A. J. Journal of Applied Photograpic Engineering, Solid
Object Generation, vol. 8, No. 4, pp. 185-188 (Dec., 1981), US.
.
Flexible Automation, Stratysys Makes 3D Models in Minutes, pp. 6-7
(Jul. 1990), US. .
Kodama, H. Review of Scientific Instruments, Automated Method for
Fabricating a Three-Dimensional Plastic Model with Photohardening
Polymer, vol. 52, No. 11, pp. 1770-1773 (Nov. 1981), US..
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Primary Examiner: Yockey; David F.
Assistant Examiner: Brooke; Michael S
Attorney, Agent or Firm: D'Alessandro; Ralph
Parent Case Text
This application is a continuation of 08/534,477, Sep. 27,1995, now
abandoned.
Claims
What is claimed is:
1. An apparatus for forming a three-dimensional object from a
material normally in a solid state but which is flowable when at or
above a flowable temperature, comprising:
a material loading module mounted to the apparatus for receiving
and rendering the material flowable;
a dispenser connected to the apparatus for selectively dispensing
successive layers of the material to form the three-dimensional
object, the dispenser being in flow communication with the material
loading module;
a platform mounted on the apparatus which is substantially
maintained below the flowablc temperature and cooperative with the
dispenser such that the successive layers are selectively dispensed
thereon,
wherein the material loading module includes a resupply receptacle
for receiving a removable container of material, the material being
in solid or partially solid phase, a heater positioned relative to
and conected to the receptacle for heating material in thc
container received in the receptacle to a molten flowable state;
the receptacle further having a fluid flow opening through which
molten material flows from the container received in the receptacle
to a reservoir in fluid flow communication with the fluid flow
opening of the receptacle, the reservoir receiving molten material
from the fluid flow opening; and
a planarizer mounted to the apparatus for removing excess material
from the successively dispensed layers, the planarized comprising a
heated member and a device to remove material from the heated
member by vaporizing material.
2. The apparatus of claim 1 further comprising a control
workstation for interfacing with an operator, the control
workstation being electrically coupled to the at least one control
computer.
3. The apparatus of claim 1 further comprising:
an X-stage coupled to the dispenser for reciprocatingly sweeping
the dispenser across the platform;
a Y-stage coupled to the platform for moving te platform
transversely to the direction of sweeping; and
a Z-stage coupled to the Y-stage for vertically moving the
platform.
4. The apparatus of claim 1 wherein the dispenser further includes
an ink jet print head.
5. The apparatus of claim 1 further comprising:
a wiper for collecting any unvaporized excess material from the
planarizer;
a collection reservoir for collecting the excess material from the
wiper, and
a material feeder line extending from the collection reservoir to
the material loading module.
6. The apparatus according to claim 1 wherein the platform is
contained within a build environment.
7. The apparatus according to claim 6 wherein the build environment
is maintained at a temperature of about 25.degree. C.
8. An apparatus for forming a three-dimensional object from a
material normally in a solid state but which may be rendered
flowable when maintained above a flowable temperature,
comprising:
a material loading module mounted to the apparatus for receiving
and rendering the material flowable the material loading module
including:
a resupply receptacle mounted to the apparatus for receiving a
removable container of material;
a heater positioned in proximity to the receptacle for rendering
the material flowable;
a reservoir functionally coupled to the receptacle for receiving
material from the removable container and for containing flowable
material; and
a dispenser for selectively dispensing successive layers of
material to form the three-dimensional object, the dispenser
including:
an ink jet print head connected to the material feed line and
including a plurality of orifices from which droplets of material
are selectively dispensed;
a planarizer for removing excess material from e successively
dispensed layers the planarizer comprising a heated member and a
device to remove material from the member by vaporizing
material;
a material feeder line coupling the reservoir to the dispenser;
and
a platform in a build environment which is substantially maintained
below the material flowable temperature and on which the successive
layers are selectively dispensed, the build environment being
maintained at a temperatur of about 25.degree. C.
9. The apparatus of claim 8 wherein the heated member is maintained
above the flowable temperature and contacts the successively
dispensed layers thereby renderng flowable at least any material
above a desired working surface.
10. The apparatus of claim 9 wherein the member further comprises a
rotating cylinder.
11. The apparatus of claim 9 wherein the member further comprises a
blade.
12. The apparatus of claim 9 wherein the member is heated to a
temperature sufficient to vaporize the at least any material above
a desired working surface.
13. The apparatus of claim 12 wherein the member further comprises
a wire.
14. The apparatus of claim 9 wherein the device comprises a vacuum.
Description
1. FIELD OF THE INVENTION
The field of the invention relates generally to systems and
associated methods for forming three-dimensional objects, and more
specifically, to the formation of three-dimensional objects from a
material which may be dispensed in a flowable state but which may
solidify or otherwise physically transform after being
dispensed.
2. BACKGROUND INFORMATION
Various approaches to automated or semi-automated three-dimensional
object production or rapid prototyping & manufacturing
("RP&M") have become available in recent years, characterized
in that each proceeds by building up three-dimensional objects from
computer data descriptive of the object in an additive manner from
a plurality of formed and adhered laminae. These laminae are
sometimes called object cross-sections, layers of structure, object
layers, layers of the object, or simply layers (if the context
makes it clear that solidified structure of appropriate shape is
being referred to). Each lamina represents a cross-section of the
three-dimensional object. Typically lamina are formed and adhered
to a stack of previously formed and adhered laminae. In some
RP&M technologies, techniques have been proposed which deviate
from a strict layer-by-layer build up process wherein only a
portion of an initial lamina is formed and prior to the remaining
portion(s) of the initial lamina at least one subsequent lamina is
at least partially formed.
According to one such approach, a three-dimensional object is built
up by applying successive layers of unsolidified, flowable material
to a working surface, and then selectively exposing the layers to
synergistic stimulation in desired patterns, causing the layers to
selectively harden into object laminae which adhere to
previously-formed object laminae. In this approach, material is
applied to the working surface both to areas which will not become
part of an object lamina, and to areas which will become part of an
object lamina. Typical of this approach is Stereolithography (SL),
as described in U.S. Reexamination Certificate No. B1 4,575,330, to
Hull. According to one embodiment of Stereolithography, the
synergistic stimulation is radiation from a UV laser, and the
material is a photopolymer. Another example of this approach is
Selective Laser Sintering (SLS), as described in U.S. Pat. No.
4,863,538, to Deckard, in which the synergistic stimulation is IR
radiation from a CO.sub.2 laser and the material is a sinterable
powder. A third example is Three-dimensional Printing (3DP) and
Direct Shell Production Casting (DSPC), as described in U.S. Pat.
Nos. 5,340,656 and 5,204,055, to Sachs, et al., in which the
synergistic stimulation is a chemical binder, and the material is a
powder consisting of particles which bind together upon selective
application of the chemical binder.
According to a second such approach, an object is formed by
successively cutting object cross-sections having desired shapes
and sizes out of sheets of material to form object lamina.
Typically in practice, the sheets of paper are stacked and adhered
to previously cut sheets prior to their being cut, but cutting
prior to stacking and adhesion is possible. Typical of this
approach is Laminated Object Manufacturing (LOM), as described in
U.S. Pat. No. 4,752,352, to Feygin in which the material is paper,
and the means for cutting the sheets into the desired shapes and
sizes is a CO.sub.2 laser. U.S. Pat. 5,015,312 to Kinzie also
addresses LOM.
Various issues arise with respect to the foregoing approaches
however. Though the approach involving a photopolymer and UV laser
has come into wide use and produces highly accurate objects, the
use of photopolymers presents handling, disposal and toxicity
issues. Furthermore, where lasers are used in any of the above
approaches, safety concerns exist.
In addition, systems embodying any of the foregoing approaches may
be generally expensive to purchase and operate because, for
example, components such as lasers and scanning mirror systems are
themselves expensive and/or need replacement or calibration over
time. Furthermore, any of the foregoing approaches may require too
much space and/or require a high level of expertise in operating
the building apparatus which may prohibit their use in a typical
office setting.
More recently, a third approach to rapid prototyping and
manufacturing has emerged whereby an object cross-section is formed
by selectively dispensing an unsolidified, flowable material onto a
working surface in desired patterns in areas which will become part
of the object cross-section. The material is then allowed or caused
to solidify or otherwise physically transform to form the object
cross-section and simultaneously adhere to the previous object
cross-section. These steps are then repeated to successively build
up the object cross-section by cross-section. A primary difference
between this approach and earlier approaches, e.g.,
Stereolithography, is that the material is typically selectively
dispensed only in those areas which will become part of an object
cross-section.
Typical of this approach is thermal stereolithography as described
in U.S. Pat. No. 5,141,680 to Almquist et al. Also typical of this
approach is Fused Deposition Modeling as described in U.S. Pat.
Nos. 5,121,329 and 5,340,433 to Crump in which a thermosettable
material is dispensed while in a molten state and then hardens
after being allowed to cool. Another example is described in U.S.
Pat. No. 5,260,009 to Penn. Another example is Ballistic Particle
Manufacturing as described in U.S. Pat. Nos. 4,665,492; 5,134,569
and 5,216,616 to Masters, in which ballistic particles are directed
to specific locations to form object cross-sections.
However, in certain of the embodiments of the patents directed to
this third approach, little detail is provided as to the actual
hardware, software or other system aspects used to implement this
approach. Furthermore, these previous embodiments may also involve
excessive noise and generally do not describe how such apparatus or
methods might be implemented to ease operation such that the
approach might be used by various personnel in an office
environment. Additionally, these previous systems and methods are
typically slow and often require trained operators.
Accordingly, there is a need in the three-dimensional modeling or
rapid prototyping and manufacturing field for a system and
associated method for forming three-dimensional objects which may
produce objects safely, easily and within an office environment.
There is a further need for this system and associated method to be
less expensive and produce objects quicker and more reliably than
previous systems or methods.
All patents referred to in this specification are hereby
incorporated by reference as if set forth in full.
3. RELATED PATENTS AND APPLICATIONS
The assignee of the subject application, 3D Systems, Inc., is
filing this application concurrently with the following related
applications, all of which are incorporated by reference herein as
though set forth in full:
Docket Application No. Filing Date No. Title Status USA-131
Concurrently Not yet Selective Deposition Pending herewith
determined Modeling Method and Apparatus for Forming
Three-Dimensional Objects and Supports USA-132 Concurrently Not yet
Method and Apparatus Pending herewith determined for Data
Manipulation and System Control in a Selective Deposition Modeling
System USA-133 Concurrently Not yet Selective Deposition Pending
herewith determined Modeling Materials and Method
Docket No. USA-131 is directed to Build and Support styles and
structures which can be used in a preferred Selective Deposition
Modeling (SDM) system based on thermal stereolithography
principles. Alternative build and support styles and structures are
also described for use in other SDM systems as well as for use in
other rapid prototyping and manufacturing systems.
Docket No. USA-132 is directed to data transformation techniques
for use in converting three-dimensional object data into support
and object data for use in a preferred thermal stereolithography
system. This Application is also directed to various date handling,
data control, and system control techniques for controlling a
preferred thermal stereolithography system
Docket No. USA-133 is directed to the preferred material used by
the preferred DSM/TSL system described herein after. Some
alternative materials and methods are also described.
The assignee of the instant application, 3D Systems, Inc., is also
the owner of a number of other U.S. Patent Applications and U.S.
Patents in the rapid prototyping and manufacturing field and
particularly in the stereolithography portion of that field. The
following commonly owned U.S. Patent Applications and U.S. Patents
are hereby incorporated by reference as if set forth in full
herein.
App. No. Topic Status 08/148,544 Fundamental elements of Thermal
Allowed Stereolithography are described. 08/484,582 Fundamental
elements of Stereolithography are Pending taught. 08/475,715
Various recoating techniques for use in SL are Pending described
including a material dispenser that allows for selective deposition
from a plurality of orifices 08/479,875 Various LOM type building
techniques are Pending described. 08/486,098 A description of curl
distortion is provide along Pending with various techniques for
reducing this distortion. 08/475,730 A description of a 3D data
slicing technique for Pending obtaining cross-sectional data is
described which utilizes boolean layer comparisons to define
down-facing, up-facing and continuing regions. Techniques for
performing cure-width compensation and for producing various object
configurations relative to an initial CAD design are also described
08/480,670 A description of an early SL Slicing technique Pending
is described including vector generation and cure width
compensation are described. 08/428,950 Various building techniques
for use in SL are Pending described including various build styles
involv- ing alternate sequencing, vector interlacing and vector
offsetting for forming semi-solid and solid objects 08/428,951
Simultaneously multiple layer curing Pending techniques for SL are
taught including techniques for correcting errors due to over
curing in the z-direction 08/405,812 SL recoating techniques using
vibrational Pending energy are described 08/402,553 SL recoating
techniques using a doctor blade Pending and liquid level control
techniques are described. 08/382,268 Several SL recoating
techniques are described Pending including techniques involving the
use of ink jets to selectively dispense material for forming a next
layer of unsolidified material. 07/182,801 Support structures for
SL are described. 4,999,143 07/183,015 Placement of holes in
objects for reducing 5,015,424 stress in SL objects are described.
07/365,444 Integrated SL building, cleaning and post 5,143,663
curing techniques are described. 07/824,819 Various aspects of a
large SL apparatus are 5,182,715 described. 07/605,979 Techniques
for enhancing surface finish of SL 5,209,878 objects are described
including the use of thin fill layers in combination with thicker
structural layers and meniscus smoothing. 07/929,463 Powder coating
techniques are described for 5,234,636 enhancing surface finish are
described. 07/939,549 Building techniques for reducing curl
distortion 5,238,639 in SL are by balancing regions of shrinkage
are described
SUMMARY OF THE INVENTION
In a first aspect of the invention, a system and associated method
for forming three-dimensional objects from a material which may be
rendered flowable is described.
In another aspect of the invention, a system and associated method
for forming three-dimensional objects in an office setting is
described.
In another aspect of the invention, a system and associated method
for removing excess material from a dispensed layer is
described.
In another aspect of the invention, a system and associated method
for rendering a building material flowable and for selectively
dispensing the flowable material to form an object is
described.
In another aspect of the invention, a system and associated method
for providing electronic control of the components used to build an
object is described.
In another aspect of the invention, user interface and control
features for a system and associated method for forming
three-dimensional objects are described.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a is a perspective view of an overall system.
FIG. 1b is a side view of an overall system.
FIG. 1c is a front view of an overall system.
FIG. 1d is a top view of an overall system.
FIG. 2 is a control system functional diagram.
FIG. 3 shows a base assembly.
FIG. 4 shows a backbone.
FIG. 5 is a schematic of a material handling module with certain
components shown.
FIG. 6 shows a bottle, receptacle and collar of a material handling
module.
FIG. 7 shows a reservoir and other components of a material
handling module.
FIG. 7a is a section view of a reservoir.
FIG. 8 shows an X-stage.
FIG. 9 shows a Y-stage.
FIG. 10 shows a Z-stage.
FIG. 11 shows a dispenser.
FIG. 11a is a side section view of a dispenser.
FIG. 11b shows a wiper.
FIG. 12 shows a dispensing path for a dispenser.
FIG. 13 shows an orifice plate with regard to a compressed bit map
representation of a layer to be dispensed.
FIG. 14 shows a control module.
FIG. 15 shows an enclosure.
FIG. 16 shows a control panel.
FIG. 17 shows a nosewiper.
FIG. 18 shows an alternative X-stage.
FIG. 19 shows an alternative material handling module.
FIG. 20 shows an alternative material handling module.
FIG. 21 shows a flat at the bottom of a bottle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Generally, the thermal stereolithography system and method of the
current invention involves building a three-dimensional object on a
layer-by-layer basis under computer control. This occurs by
dispensing successive layers of a building material which is
rendered flowable upon application of some form of synergistic
stimulation such as heat or other form of energy which may
transform the material's state. Representative building materials
include thermoplastic materials which are preferably nontoxic, and
the disposal and handling of which are preferably not governed by
restrictive government regulations. Preferably, materials such as
those described in U.S. Pat. No. 5,855,836 are utilized, however
this invention is in no way intended to be limited to such
materials.
While in such a flowable state, the building material may be
selectively dispensed from a dispenser to some or all of the areas
of successive layers which are to comprise successive object
cross-sections and support regions. After a given object layer is
dispensed, it is allowed or caused to solidify or otherwise
physically transform so as to form the object and support
cross-section corresponding to that layer. A successive layer of
material is then selectively dispensed onto and adhered to the
preceding cross-section. As this subsequent layer solidifies or
otherwise physically transforms, it forms the next object and
support cross-section. This process is repeated until all object
cross-sections have been formed thereby completing the object.
As noted, this building method advantageously avoids the use of
lasers, toxic chemicals, complicated stamping machinery or other
apparatus which may be expensive, noisy or too large, as well as
dangerous if mishandled. Because this building method is preferably
carried out in a relatively simple fashion, the current invention
may be advantageously used in a typical office environment by
various operators.
An overview of several primary aspects of a first embodiment of the
current invention is now provided, which is then followed by more
detailed discussion. A schematic of the overall system 10 is shown
in FIG. 15, but reference is now made to FIGS. 1a-1d which show
several of the components contained therein. As shown in FIG. 1a,
system 10 may generally include control workstation 20, into which
the CAD design of the object may be input such as STL or other
building files, and printer 40 in which the object is built.
Workstation 20 may include keyboard 22 and monitor 24 for the entry
and display of appropriate commands and user prompts. Workstation
20 may comprise a personal computer and/or UNIX operating system or
other appropriate computer equipment which may already exist at the
operator's facility prior to the arrival of printer 40. Workstation
20 may then interface, via Ethernet or other appropriate media,
with control computer 26 which may be located in printer 40.
Generally, control computer 26 receives signals and building
commands from workstation 20 and in turn controls the various
electronics and other components of printer 40. To accommodate
office space constraints, control workstation 20 may be attached to
printer 40 or may be located remotely thereto.
To this end, it is preferred that after the computer design of the
object has been input into workstation 20, the operator of printer
40 need not necessarily further interface with workstation 20, but
may need only input building parameter information on control panel
267 as shown in FIGS. 15 and 18. For example, the operator may push
appropriate buttons on control panel 267 to dictate various
building parameters such as: the number of objects to be built, the
dispenser and material to be used when multiple dispensers and or
materials are incorporated into system 10, the desired resolution
of the object, and other building parameters such as whether the
object will be solid or hollow. Commands may alsc be input via
control panel 267 to allow the operator to run a test so that the
material dispenser may be tested before building an object. Other
commands may be input and these are discussed in detail later.
Based on these inputs, control computer 26 then preferably
transmits appropriate commands to the various components of printer
40 so that the object is built in desired fashion. This provides
the benefit that the operator need not be intimately familiar with
CAD, specific building commands, techniques or the like, thereby
enabling various office personnel to build objects. Rather, the
operator preferably need only input general building information,
somewhat similar to one operating an office photocopying
machine.
As shown in FIGS. 1a-1d, printer 40 may generally include material
handling module 60, building module 90 and control module 200. Each
module is described in more detail later, but for purposes of
overview, material is generally loaded in material handling module
60 at which point heat or other synergistic stimulation may be
added to render the material flowable. The flowable material may
then be directed to building module 90 where the object is built on
platform 92. Control module 200 preferably contains the various
circuit boards and other mechanisms which may control the operation
of printer 40. Modules 60, 90, 200 need not be separated by walls
or the like as it is preferred that the building process occur at a
temperature, such as ambient, that is suitable for operation of the
various components in control module 200. Excess material left over
from the building process may also be recovered and redelivered
back to material handling module 60 for disposal or recycling.
To build an object, successive layers of building material are
selectively dispensed from dispenser 94, starting with a layer
which may be dispensed directly onto platform 92, and then with
material layers being dispensed onto the preceding
layer/cross-section. To form a layer, dispenser 94 may sweep back
and forth along X-stage 96 so that dispenser 94 travels above and
across platform 92. For each pass, dispenser 94 preferably
dispenses material only at those locations which will comprise an
object cross-section or supports therefor.
Between each pass or group of multiple passes of platform 92 along
X-stage 96, platform 92 may be incrementally moved along Y-stage
98, i.e., in the direction transverse to the sweep direction of
dispenser 94. This allows dispenser 94 to successively dispense
material on adjacent transverse areas so that material may be
selectively dispensed over the entire area of the layer being
formed. After a layer is dispensed, platform 92 may be lowered
relative to dispenser 94 along Z-stage 100 in preparation of
forming the next layer. This procedure is then repeated until the
object is completed.
Generally, operation of the components associated with the material
and building modules 60, 90 are controlled by various printed
circuit boards and other control components which may be contained
in control module 200 and/or other locations. To control the
building process, control computer 26 generally receives signals
from workstation 20 and control panel 267 as well as feedback
signals from material and building modules 60, 90. These signals
are then processed and transmitted to the various building
components.
As shown in more detail in FIG. 15, system 10 may include enclosure
250 which covers the interior components to provide an
aesthetically pleasing system suitable for an office environment.
As discussed later, enclosure may also serve to squelch noises
produced by the building operation and preferably includes various
access to doors to access components therein, and windows to view
the building process as it occurs.
The overall control configuration of system 10 is now described
with reference to FIG. 2 which shows the routing of various control
signals in system 10. It should be noted that components in
addition to those shown in FIG. 2 may be included in printer 40 and
that FIG. 2 is not intended to be limiting in this regard.
Following this overall control description, the components of
system 10 are discussed in more detail.
As shown, any commands not available on the provided control panel
267 are input into control computer 26 from workstation 20. Control
computer 26 may comprise a personal computer or other suitable
means of control. The connection to control computer 26 may be via
an ethernet, but alternative communication media may be used.
Control computer 26 may transmit control signals to digital signal
processor board ("DSP") 204, but alternatively, control computer 26
may be subsumed into DSP 204. Control computer 26 may also transmit
control signals to services board 222 which transmission may occur
directly or through DSP 204.
Generally, DSP 204 may control the motion of dispenser 94 and the
dispensing of material therefrom, as well as the motion of X-stage
96, Y-stage 98 and Z-stage 100. Services board 222 may control the
various heaters described below, as well as other maintenance type
of functions of printer 40.
In addition, a logic board (not shown) may provide communication
between control computer 26 and DSP 204 by processing signals from
control computer 26 into a form suitable for utilization by DSP
204. The logic board may also provide communication between control
computer 26/DSP 204 and workstation 20/control panel 267. DSP 204
may then transmit control signals to services board 222. In
addition, an input/output board (not shown) may provide
communication between control computer 26 and services board
222.
DSP 204 may send control signals through services board 222 and on
to various components to control their movement. For example, DSP
204 may send signals to head driver board 206 to control various
components of dispenser 94 such as the print head 206a when an ink
jet print head is used to dispense material, planarizer 206b and
part cooling fan 206c. These components are discussed in more
detail later. DSP 204 may also send signals to planarizer motor
207.
DSP 204 may also control the X-, Y- and Z-stages by sending control
signals to X-amplifier 208, Y-amplifier 210 and Z-amplifier 212.
After the signals are amplified, they are transmitted to the X, Y
and Z motors 208a, 210a and 212a respectively which in turn effect
movement of the various stages, i.e., sweeping movement of
dispenser 94 along X-stage 96, movement of platform 92 along
Y-stage 98 between dispenser sweeps and movement of platform 92
along Z-stage 100 after a layer is dispensed.
As shown, printer 40 may include X-, Y- and Z-encoders 214, 216 and
218 which indicate the positions of dispenser 94 along X-stage 96,
platform 92 along Y-stage 98 and platform 92 along Z-stage 100
respectively. Signals representing these positions may then be
transmitted along servo loop 220 back to DSP 204 for any
appropriate adjustment of position along the X-, Y- or Z stages 96,
98 and 100.
For example, DSP 204 may control the motion of platform 92 along
Z-stage 100 and also receive position feedback control loop signals
to adjust and correct platform 92 position. Feedback signals may
also be provided by a Z-limits component to advise when platform 92
should be returned to its original position, which signals may be
controlled by DSP 204. Servo loop 220 may be enclosed in software
but it is anticipated that such control may be effected through
hardware and/or a combination of software and hardware.
Position information may also be used to determine the position of
the scanning print head. This print head position information may
be used to determine drop sites for dispensing of building
material. In this method, drop sites are determined spatially. In
the alternative, if the scanning velocity and acceleration are
known or can be determined, time may be used as the variable for
determining drop site locations.
Services board 222 may also provide signals to control various
components associated with material handling module 60. For
example, services board 222 may provide signals to bulk feed relays
and connections 223. Signals are then in turn provided to vacuum
regulator 223a, bulk feed 223b, waste collection 223c and nosewiper
223d which components essentially serve to pump flowable material
from material handling module 60 to building module 90 and to
return excess material to material handling module 60. These
components are discussed later.
Services board 222 may also transmit signals to control other
components. As shown in FIG. 2, services board 222 may transmit
signals to activate or inactivate any of several heaters 224 which
may be contained in printer 40. For example, a heater may be
activated which applies heat to material contained in material
handling module 60, to render the material flowable and ready for
transport to building module 90. To this end, thermistor 226 may be
included in the control loop to provide temperature feedback
information to services board 222 so that the heater may be
inactivated and activated as necessary.
Services board 222 may also control any of several interlocks 228
which may be included in printer 40. As described later, interlocks
228 may be used to automatically turn off printer 40 for safety
purposes if, for example, the handle 260 of access door 256 (as
shown in FIG. 15) to building module 90 is opened during object
formation. Services board 222 may also control other components
such as cooling fans 230 which may be used to cause just-dispensed
material to physically transform and/or to cool other portions of
printer 40. Services board 222 may also control the lights 232
associated with control panel 267 or other LCD displays of printer
40.
Reference is now made to FIGS. 1a-d and 3-11 which show printer 40
at various levels of detail and/or various components thereof. FIG.
3 shows base assembly 42 which may support printer 40. Base
assembly 42 preferably includes wheels 44 so that printer 40 may be
easily transported, e.g., from office to office. Base 42 preferably
includes leveling feet 41 which may provide stationary support for
printer 40 by lifting printer 40 slightly off of wheels 44. This
avoids a possible decrease in object resolution which might
otherwise occur due to movement of printer 40 caused by the
acceleration/deceleration of dispenser 94 or by vibration of the
entire printer 40. It is also preferred that the object be built
while printer 40 is level. Alternatively, each wheel 44 may include
a foot pedal (not shown) which may be depressed when printer 40 is
stationary thereby raising wheels 44 slightly above the floor.
Preferably, base assembly 42 comprises a series of struts 48 which
may be made of 0.318 cm cold-rolled steel to provide overall
rigidity to system 10 to help maintain object resolution and
dimensional accuracy during the building process. However, other
support methods and materials may be used. Base 42 may also include
multiple struts 48 to add rigidity. Struts 48 may be hollow to
provide channels for the mounting of various cables (not shown)
used in printer 40 as well as to optimize strength to weight.
FIG. 4 shows backbone 50 to which various components of printer 40
may be attached. The bottom 52 of backbone 50 may be coupled to
platform 46 of base 42 shown in FIG. 3. Preferably, backbone 50
comprises cast aluminum to reduce the weight of printer 40, to
provide rigidity to dampen the inertial forces arising as dispenser
94 accelerates and decelerates at either end of its sweeps across
platform 92, as well as to reduce overall costs. To this end,
backbone 50 may weigh approximately 59 kg. Preferably wire
feed-through(s) 54 are incorporated into the backbone 50 for cables
and the like.
Also located in proximity to base 42 may be material handling
module 60 which is now discussed in further detail with reference
to FIGS. 1a-d, 5-7, 7a and 15. As shown in FIG. 5, material
handling module 60 may include receptacle 64 for receiving bottle
66 containing material to build the object. Bottle 66 is referred
to as a bottle for descriptive purposes only, any suitable
container or vessel may be used. Attached to the bottom of
receptacle 64 may be collar 68. Receptacle 64/collar 68 may be
positioned over reservoir 70.
Building material may be supplied from reservoir 70 via feeder line
72 to building module 90. Material handling module 60 may also
include waste reservoir 86 which may collect excess material from
building module 90 via feeder line 87. The material collected in
waste reservoir 86 may be recycled or disposed of.
As shown in FIG. 6, receptacle 64 is preferably configured to
receive bottle 66. Receptacle 64 may be hingeably attached to door
252 of enclosure 250 via brackets 65 and a four-bar linkage (not
shown) or other attachment means. Collar 68 may be sealed and
attached to receptacle 64 via epoxy, bolts or other attachment
means. Collar 68 also preferably includes heater 78 such as a
cartridge heater manufactured by Watlow, Inc. As described below,
heater 78 serves to render the material contained in bottle 66
flowable. Collar 68 may also include recess 69 to accommodate the
bottom of bottle 66. Reservoir 70 may be mounted to base 42 and as
shown in FIG. 5, receptacle 64/collar 68 may be positioned over
reservoir 70 so that the bottom of collar 68 is over and/or within
reservoir trough 88 shown in FIG. 7.
To load printer 40 with material, enclosure door 252 may be opened
to provide access to material handling module 60. To this end, door
252 may be hinged at its bottom to enclosure 250 so that when
opened, the top of receptacle 64 tilts outward and is directly
accessible to the operator. Preferably, door 252 includes some type
of linkage to control the amount it may be opened and to hold door
252/receptacle 64 in a stationary position when bottle 66 is
inserted into receptacle 64.
While in bottle 66, the material is generally in a solid state and
may comprise one solid mass or more preferably, a collection of
prills or beads. It is preferred that bottle 66 comprise a material
such as polypropylene that will not react with the material
therein. This provides that bottle 66 has a sufficient shelf life
before being loaded into printer 40. Other suitable materials may
be used for bottle 66 however.
Bottle 66 may contain a volume of about 3.79 liters so that when a
typical building material is used, bottle 66 weighs about 2.27 kg
when full. This weight may be relatively easily handled by various
operators in an office environment. Other bottles containing
greater weights of material may be used but it is generally
preferred that a full bottle 66 weigh 5 kg. or less. Bottle 66
preferably also includes cap 67 which may be grasped by the
operator to ease material loading, and it is preferred that cap 67
include some type of handle for easy handling.
The interior of bottle 66 is preferably concave to facilitate the
flow of material therefrom. The outside of bottle 66 is preferably
angled as shown in FIG. 6 to facilitate insertion into receptacle
64. Also, the dimensions of bottle 66 preferably correspond with
the inside dimensions of receptacle 64 and collar 68 to provide a
secure fit. Receptacle 64 may also include gasket 62 which may
comprise rubber or some other flexible material. Gasket 62 is
generally pushed downward when bottle 66 is inserted and then pops
back up and over part of the top of bottle 66. This further ensures
a secure fit between bottle 66 and receptacle 64.
As bottle 66 is inserted into receptacle 64, the corresponding
dimensions therebetween serve to guide bottle 66 downward toward
collar 68. As the bottom of bottle 66 fits into recess 69, it is
preferably pierced by one or more pins 71 that may be attached to
collar 68. To facilitate suitable piercing, the portions of the
walls of the bottom of bottle 66 where pins 71 are intended to
penetrate may be thinned or fitted with easy pierce locations. The
base of bottle 66 is designed from a material which may be pierced
without undue effort and without bottle fracture. The operator may
then continue to insert bottle 66 into receptacle 64/collar 68
until it is seated therein, and may then close door 252.
When seated, the bottom of bottle 66 is preferably located over the
hole in reservoir trough 88. At this time, the heat provided by
heater 78 is conducted through collar 68 and/or receptacle 64 so
that heat impinges on bottle 66 to render the building material
flowable. To facilitate this heat transfer, bottle 66 preferably
comprises a thermally conductive material. Additionally, collar 68
and receptacle 64 may comprise aluminum or other heat conductive
material. Gasket 62 also serves to contain any heat which might
otherwise escape through the area around the top of bottle 66.
As the building material in bottle 66 becomes flowable, it flows
downward through the holes created by pins 71. The flowable
material may then be guided by collar channels 73 to and through
collar filter 75 which may be mounted at the bottom of recess 69
and which may comprise a perforated metal sheet. Other types of
filters may be used however. At this point, the material flows into
reservoir 70 which is shown in FIG. 7. Gravity thus facilitates
material traveling into reservoir 70 which travel might otherwise
be hindered due to viscosity effects.
When door 252 is closed, receptacle 64 and thus bottle 66 are
preferably positioned at an angle relative to vertical so that as
bottle 66 empties, material continues to flow through at least one
of the holes created by pins 71. This may avoid "puddles" being
formed in the bottom of bottle 66 which could lead to material
being wasted. As can be seen from FIG. 5, receptacle 64 need not
directly attach to reservoir 70. Rather, receptacle 64 is
preferably positioned so that bottle 66 substantially aligns over
the hole in reservoir trough 88.
The heating provided by collar 68 is now further described. Heater
78 is preferably housed by a cylindrical bore or other cavity in
collar 68. Alternatively, heater 78 may be mounted to the exterior
of collar 68. To render the material flowable, heater 78 may be
heated in the range of about 70-130 degrees Celsius.
Collar 68 also preferably includes thermistor 77 and fuse 79 which
serve to control heater 78. That is, thermistor 77 may send
temperature information to services board 222 as shown in FIG. 2.
If the temperature information reflects a temperature which is too
high, i.e., the temperature exceeds the range desired to render the
material flowable, services board 222 may send a control signal to
inactivate heater 78. Similarly, thermistor 77 may send information
to services board 222 indicating that heater 78 should be
activated. Fuse 79 may serve as an automatic safety turn-off. That
is, if a certain temperature is reached in collar 68 but heater 78
has not been inactivated via thermistor 77 and services board 222,
fuse 79 may itself inactivate heater 78.
For safety purposes, door 252 may be solenoid activated so that it
may be opened only when receptacle 64 and/or bottle 66 have
sufficiently cooled so that the operator is not burned when trying
to remove bottle 66. To this end, receptacle 64 may include one or
more thermistors (not shown) which provide temperature information
to services board 222. In turn services board 222 may send signals
to the solenoid (not shown) to either permit or prevent the opening
of door 252. As an additional safety precaution, the exterior of
receptacle 64 may be insulated with a two-part foam to protect
against burns should the operator nonetheless contact these
components when they are heated.
Reservoir 70 is preferably maintained at a temperature sufficient
to keep the viscosity of building material low enough so that it
may be pumped through feeder line 72 to building module 90. As
shown in FIG. 7, one or more heaters 76 may be incorporated into
reservoir 70 to maintain the material temperature in the flowable
range. Suitable heaters 76 may be cartridge heaters manufactured by
Watlow, Inc. When the building material comprises a preferable
thermal stereolithography material, reservoir 70 is preferably
maintained at a temperature of about 90 degrees Celsius. To
facilitate heat transfer from heaters 76 to the building material,
reservoir 70 may comprise aluminum or other thermal conductive
material.
Thermistor(s) 78 may be placed in or adjacent reservoir 70 to
provide temperature feedback information to services board 222 as
shown in FIG. 2. In this manner, heater(s) 76 may be activated as
necessary to maintain the desired material temperature, and also
inactivated when not needed to reduce power consumption.
Preferably, reservoir 70 may contain a volume of about 7 liters of
building material which is sufficient to form objects weighing
about 5.5 kg. This size of reservoir 70 is adequate to receive
approximately two bottles of material and also adequate to allow
printer 40 to operate over a period of time while unattended, e.g.,
over a weekend. Though reservoir 70 is shown to be somewhat
rectangular, it may assume other shapes.
Should reservoir 70 already be full when bottle 66 continues to
drain, reservoir trough 88 may receive an additional volume of
material. If reservoir 70 and trough 88 are both full when bottle
66 continues to drain, tray 89 may collect any material that flows
over and down the sides of reservoir 70. Tray 89 may comprise
polypropylene but other materials may be used.
When initially setting up and using printer 40, several bottles 66
of building material may be consecutively fed into material loading
module 60 to "prime" printer 40 so that the material level in
reservoir 70 may be raised to a desired minimum level such as that
which is aligned with sensor 80 as shown in FIG. 7. When material
is later drawn from reservoir 70 by pump 81, if the material level
falls below sensor 80, sensor 80 may send a signal to services
board 222 to activate heaters 78 in collar 68 to melt more material
in bottle 66 to replenish reservoir 70. When bottle 66 is empty, it
may be removed and replaced with a full bottle 66.
As a safeguard, reservoir 70 may include an emergency shut-off
material level sensor 82 which may be located below sensor 80 but
above the floor of reservoir 70. Sensor 82 serves to prevent
material depletion or near material depletion in handling module 60
by shutting off printer 40 should the material fall therebelow.
Material depletion or near material depletion is preferably avoided
to prevent the situation where only a small volume of material is
flowing from reservoir 70, through line 72 and out of dispenser 94.
This is because it has been determined that when only a small
volume is flowing, the material tends to adhere or "carmelize" onto
the interior of reservoir 70, feeder line 72 and dispenser 94. Such
carmelization ultimately results in the blocking of line 72 as well
as other components.
On the other hand, it should be noted that there is not a major
concern that air bubbles may form in feeder line 72. Though this
may lead to temporary sporadic dispensing of material from
dispenser 94, it is not viewed as damaging as is carmelization.
To help avoid material depletion, the operator may view reservoir
70 through window 254 in door 255 of enclosure 250, but preferably,
sensor 80 provides an audible signal, in addition to initiating the
melting of additional material in bottle 66. And as indicated
above, sensor 82 preferably shuts off printer 40 by an appropriate
control signal to services board 222 should that lower level be
reached. Sensors 80 and 82 may be of the type manufactured by
Spectra, Inc.
Another feature providing information reflecting the volume of
material remaining in reservoir 70 is now described. As shown in
FIG. 7, one end of reservoir 70 is mounted to pivot 61 while the
other end is mounted on spring 63. Optical sensor 63a may be
mounted in proximity to reservoir 70 as shown.
As material is drawn from reservoir 70 thereby reducing its weight,
spring 63 pushes up on its end of reservoir 70 which causes
reservoir 70 to rotate about pivot 63. To this end, the
compressibility of spring 63 is preferably matched with the weight
of reservoir 70 along with the material. The position of the one
end of reservoir 70 is measured by optical sensor 63a, and based on
this position along the scale included in sensor 63a, calculations
may be performed which reflect the volume of the material
remaining. This information may then be sent to control panel 267
for a readout of the remaining material volume. Preferably, spring
63 is positioned and its compressibility is such that when fully
extended, reservoir 70 is level and the material level is at the
level of emergency sensor 82.
As a safety precaution, door 255 may include an interlock (not
shown) that is coupled to services board 222, such that if door 255
is opened, printer 40 and heaters 76 are inactivated. It should
also be noted that reservoir may be insulated with a two-part foam
to protect against burning if touched by the operator. In any
event, it is intended that door 255 not be easily removed.
The transfer of material from reservoir 70 to building module 90 is
now further described. Reservoir 70 preferably includes pocket 83
which is essentially a trecessed portion in the reservoir floor. It
is the material in pocket 83 which is pumped to building module 90.
As shown in FIG. 7, heaters 76 may be located in proximity to
pocket 83 which represents a relatively small volume of material to
heat, thus ensuring that the material about to be pumped to
building module 90 is sufficiently flowable. A filter 85 may extend
across and over pocket 83 to further ensure that material being
pumped to dispenser 94 is free of contaminants. A suitable filter
may comprise stainless steel 100 mesh but other filters may be
used.
The pumping of material occurs via the vacuum formed by pump 81
which draws material from pocket 83. Pump 81 may include a piston
(not shown) which may be powered by motor 81a. Preferably, material
is drawn from pocket 83 through a one-way check valve 84 so that
material only flows out of reservoir 70. In this manner, when the
piston travels away from reservoir 70, check valve 84 opens and
allows material to be drawn. When the piston travels towards
reservoir 70, check valve 84 closes and a second check valve 84a
may open to allow air to escape from pump 81. Additional material
is then drawn through valve 84 when the piston travels away. Before
entering check valve 84, the material may pass through filter 85'.
A preferred filter is a synthetic filtering media such as that
manufactured by Gelman Sciences which has pores of about five (5)
microns..
Pump 81 provides a volumetric flow of about 0.5 cubic centimeters
per stroke. A flow in this range is preferred so that the amount of
building material provided to dispenser 94 is neither too much so
as to flood dispenser 94, nor too little so as to help avoid
forming air bubbles. Pump 81 may be powered by a 24 DC volt motor
81a having a 6:1 ratio such as that manufactured by Halbar
Associates.
After leaving pump 81, the material may then travel through line 55
which in turn may enter a bore or other passageway 56 within the
reservoir wall as shown in FIGS. 6, 7 and 7a. Passageway 56 as seen
in FIG. 7 advantageously maintains the flowability of the building
material as the reservoir walls will typically be heated due to
conduction of heat provided by heaters 76 through the material in
reservoir 70. Thus, additional heaters may be unnecessary at this
location. Passageway 57 seen in FIG. 7a may then lead into cavity
58 which may comprise a circular recess in the reservoir wall.
Cavity 58 may include filter 59 which ensures that the material is
free from contaminants before entering feeder line 72 en route to
building module 90 Cavity 58 may also be encapsulated by cover 51
which has a port 53 connected to feeder line 72
Feeder line 72 may extend from reservoir 70 to dispenser 94 of
building module 90. Feeder line may comprise a TEFLON tube having
an internal heated coil to maintain the flowability of the material
as it passes through. It is preferred that feeder line 72 be
flexible and resilient to withstand repeated flexing or other
movement due to the sweeping motion of dispenser 94. Because of the
voltage associated with heating feeder line 72, insulation is
preferably placed on its end as a safety precaution. It is
preferred that feeder line 72 be maintained at about 125 to 135
degrees Celsius.
For purposes of diversity in object formation capability, material
handling module 60 may comprise multiple reservoirs 70 and a
plurality of the components supplying material to reservoirs 70 to
provide supplies of different materials to building module 90. To
this end, multiple feeder lines 72 may extend from material
handling module 60 to building module 90. The different materials
may have varying properties such as color, rigidity, conductivity
and the like so that the object may be customized according to
particular needs.
In summary, the material handling module 60 essentially
contemplates a three-stage situation where (1) solid material may
be stored while waiting to be rendered flowable, e.g., in bottle
66, (2) flowable material is stored awaiting delivery to dispenser
94, e.g., in reservoir 70 and (3) flowable material exists where it
awaits dispensing, e.g., in dispenser 94.
As shown in FIG. 15, enclosure 250 may include a door 252 for
physical access to receptacle 64 for loading a bottle 66 of
material. Door 252 may also include a window (not shown) to provide
visual access to bottle 66 and receptacle 64. For aesthetic and/or
safety purposes, doors 252, 253 and 255 may themselves all be
covered by another door to provide a unitary door appearance and
protection against hot temperatures. As an alternative, material
handling module 90 may be coupled to a slide mechanism (not shown)
which is in turn coupled to base 42 so that module 60 may be slid
forward out of enclosure 250 to facilitate servicing or other
inspection.
Referring now to FIGS. 1a-d and 8-11, building module 90 is now
further described. As shown in FIG. 1c. feeder line 72 extends from
material loading module 60 to building module 90 at which point
feeder line 72 enters dispenser 94. In a preferred embodiment,
dispenser 94 comprises an ink jet print head as discussed in more
detail later. To accommodate different building materials,
dispenser 94 may have multiple ports (not shown) to receive
multiple feeder lines 72 from material handling module 60.
Dispenser 94 may be attached to X-stage 96 and moves back and forth
over platform 92 during which it dispenses material to form
successive layers of the object. The X, Y and Z stages referred to
earlier are now described in more detail with reference to FIGS. 8,
9 and 10 respectively.
X-stage 96 may generally comprise belt drive system 104 which
provides the reciprocating sweeping movement of dispenser 94 across
platform 92. Dispenser 94 may be attached to belt drive system 104
via plate 106. X-stage 96 may be mounted to surface 56 of backbone
52 via rails 120, or alternatively, some other type of mount (not
shown). As shown, one end of belt 110 is coupled to motor 112 while
the other end is fitted around pulley 114. Plate 106, and thus
dispenser 94, may be attached to belt 110 via brackets 116. Slide
bearings 118, which are also mounted to plate 106, slide along
rails 120 to provide precise linear movement in the X-direction. A
preferred slide bearing 118 is model no. LXPB-1018-125A as
manufactured by LM 76, Inc. and a preferred rail 120 is that such
as manufactured by Thompson, Inc. A preferred motor 112 is Dynetic
Systems model no. MS 3130.
In operation, motor 112 preferably provides rapid acceleration and
deceleration at either end of dispenser's 94 travel. Motor 112 and
its direct drive pulley 113 coupled to belt 114 rotate in one
direction to provide a sweep of dispenser 94 over platform 92 until
the other end of X-stage 96 is reached. Motor 112 then rotates the
other direction to provide a return sweep. This process
reciprocates for successive sweeps.
A preferred velocity of dispenser 94 along X-stage 96 is about 33
cm/sec. This represents a sufficiently large velocity so that
material is dispensed quickly enough to provide reasonable build
times. However, this also represents a small enough velocity so
that the associated accelerations and decelerations of dispenser 94
occurring at either end of X-stage 96 are not so large as to cause
significant inertial forces. Such inertial forces are preferably
avoided because if they are not sufficiently dampened, they could
impact dispensing and object accuracy. Where dispenser 94 comprises
an ink jet print head, the velocity of about 33 cm/sec. also
represents a slow enough sweep velocity such that about 1200 drops
of material per inch, i.e., 472 drops per centimeter, may be
dispensed.
It is also preferred that X-stage 96 move platform 92 with a
resolution of 300 counts per inch, i.e., 300 pixels per inch or 118
pixels per centimeter as described later, such that 4.times.
overprinting results in 1200 drops per inch, i.e., 472 drops per
centimeter. To this end, X-stage 96 may include encoder 121 which
may comprise an etched mylar strip, and encoder reader 122 which
provides position information to DSP 204 as shown in FIG. 2 for
adjustment purposes. Where dispenser 94 comprises an ink jet print
head, the firing of the ink jets is based on the position
information from encoder reader 122. As discussed in more detail
later, material is dispensed from dispenser 94 in both directions
of travel along X-stage 96.
Referring now to FIG. 9, Y-stage 98 is now described. Y-stage 98
may be mounted to Z-stage 100 via rail mounts 123. This mounting
arrangement is shown in FIGS. 1b and 1c. Platform 92 (not shown in
FIG. 9) may be mounted to Y-stage 98 on slide 128. Thus the
vertical movement of Z-stage 100 also effects Z-direction movement
of Y-stage 98 and platform 92. As mentioned above, Y-stage 98
serves to move platform 92 an incremental distance in the direction
perpendicular or transverse to the X-direction each time dispenser
94 reaches either end of its movement along X-stage 96. This
provides that on the next sweep of dispenser 94, material will be
deposited on an adjacent area of that layer or other portion of
that layer onto which material has not yet been dispensed.
As shown in FIG. 9, Y-stage 98 may include a ball screw system 124
of the type manufactured by Nook, Inc. Ball screw 124 may include
screw 126 which threadably engages nut 127. Screw 126 may be
coupled to motor 132 via direct drive and nut 127 may be coupled to
slide 128 via nut block 129. To effect Y-direction movement of
slide 128 along rails 130, screw 126 is rotated by motor 132.
Because nut 127 does not rotate, the pitch of the threads on screw
126 effects linear movement of nut 127 which in turn effects linear
movement of nut block 129, slide 128 and thus platform 92. Slide
128 may also be coupled to guide blocks 125 which slide along rails
130 to provide smooth motion of platform 92.
It is preferred that Y-stage 98 moves platform 92 the desired
transverse distance and then settles when dispenser 94 reaches
either end of X-stage 96 and before dispenser 94 begins its next
sweep along X-stage 96. It is preferred that motor 132 provides
rotation such that slide 128, and thus platform 92, may travel at
1.57 cm/sec. with an acceleration of 0.3 g.
It is also preferred that motor 132 provide rotational accuracy so
that Y-direction movement has a resolution of 0.000254 cm. To this
end, Y-stage 98 may include encoder 134 and read head 135 which
provides position information to DSP 204 as shown in FIG. 2 for
adjustment purposes. Encoder 134 may comprise an etched glass scale
such that when the light from read head 135 shines on an etch, a
positioning signal is sent to DSP 204. Preferably, Y-stage 98 is
configured so that it may travel about 22.86 cm in the Y-direction
so that printer 40 may build objects of various transverse
dimensions.
Y-stage 98 may also include bellows 131 which serve to cover many
of the moving and other parts of Y-stage 98 to prevent them from
being contaminated by building material, dirt or other foreign
substances. Bellows 131 are preferably flexible but resilient to
withstand repeated movement of slide 128.
Referring now to FIG. 10, Z-stage 100 is now described. As
mentioned above, Z-stage 100 is lowered relative to dispenser 94 an
incremental distance after each layer is deposited. The incremental
distance may be one layer thickness which may be in the range of
approximately 1.2-1.5 mils, i.e., 0.003-0.004 cm, but may also be
larger. It is preferred that Z-stage moves and settles before
dispenser 94 makes its next sweeps along X-stage 96. After the
object is completed, Z-stage 100 may raise platform 92 to its
original position. At other appropriate times, Z-stage 100 may also
move platform 92 to a "store" position which is away from dispenser
94 so that dispenser 94 may be easily inspected. Z-stage 100 may be
mounted to backbone 50 via bracket 136 and rail spacers 137.
Y-stage rail mounts 123 may be mounted to Z-stage 100 on mounting
surfaces 138 and ball screw system 124 of Y-stage 98 may be mounted
to Z-stage surface 139.
Z-stage 100 may include acme screw system 140 wherein screw 142
threadably engages nut 143 which is coupled to motor 146. Motor 146
is coupled to slide 144 which includes flange 145 which in turn
supports Y-stage 98. In this arrangement, screw 142 may not rotate
and may remain stationary. However, nut 143 may be rotated by motor
146 and the pitch of the threads effects Z-direction movement of
nut 143 which moves motor 146 up or down. This in turn effects
linear movement of slide 144, Y-stage 98 and platform 92. A
preferred motor 146 is model no. LA42BLKL-300 manufactured by
Eastern Air Devices, Inc. Z-stage 100 may include bellows 147 to
protect the moving and other parts from contamination. Z-stage 100
may also include rolling loop 149 which may accommodate the
vertical movement of Z-stage 100 and which may serve as a cable
guide.
Z-stage 100 may include rails 148 along which bearings 150 slide.
Bearings may be mounted to slide 144 and thus help guide the
vertical movement of Z-stage 100. Preferably, Z-stage 100 may be
linearly moved at a velocity of about 0.381 cm/sec. and a
resolution of 0.000254 cm. For accuracy purposes, Z-stage 100 may
also include encoder 152 which may comprise etched glass and read
head 153 which provides position information to DSP 204 as shown in
FIG. 2 for adjustment of Z-stage motion. Z-stage may also be
capable of moving an overall amount about 22.86 cm which allows
printer 40 to build objects of varying heights.
The dispensing of material to form the object is now discussed in
more detail with reference to FIGS. 1a-1d and 11-13. Generally, it
is preferred that the object be rapidly built. To this end, it may
be preferred to have dispenser 94 sweep along X-stage 96 only as
far as the boundaries of the object to be formed rather than
sweeping the entire length of X-stage 96. In any event, building
preferably occurs so that the object replicates the geometry of the
original data, e.g., CAD data, as accurately as desired. It is also
preferred that the resulting object is aesthetically pleasing with
a minimum of surface blemishes and irregularities. In any event,
building speed may be varied according to the accuracy desired.
Dispenser 94 may comprise various embodiments. A preferred
embodiment which is described in more detail below is a modified
ink jet print head 102. Alternatives include nozzles, single and
multiple orifice dispensers and other types of feed systems which
are capable of dispensing flowable material. It if preferred that
any alternative for dispenser 94 be capable of selectively
dispensing material under computer control.
One embodiment of dispenser 94 is shown in FIG. 11 in which
dispenser 94 is coupled to X-stage 96 via plate 106. In this
embodiment, dispenser 94 includes dispensing platform 154 on which
is mounted an ink jet print head 102. A preferred wave causes a
drop of material to be emitted from the orifice 156. As shown in
FIG. 2, the electric firing pulses to print head 102 (206a in FIG.
2) are provided by head driver board 206 which in turn may be
coupled to DSP 204 and control computer 26. This control mechanism
provides signals dictating the rate and timing of the firing pulses
applied to the individual orifices 156. Material may be dispensed
from orifices 156 in each direction of dispenser's 102 movement
along X-stage 96.
Because each droplet will have an X-direction component of velocity
as it travels from print head 102 towards platform 92 or the prior
layer on which it will land, the signal causing the emission of a
droplet may be provided to orifice 156 before the desired landing
location is actually reached. This "pre-firing" provides correction
for the droplet's time of flight and thus enhances object building
accuracy. This pre-firing capability may be provided by software,
i.e., software which receives position information from Y-encoder
121 and X-encoder reader 122.
The array of orifices 156 are generally maintained at a temperature
of about 120 to 130 degrees Celsius so that the material being
dispensed remains flowable to avoid clogging which might otherwise
occur. Heaters 160 may be included in proximity to orifices 156 as
well as the back end of print head 102 for this purpose. Building
module 90, i.e., the area around the platform is generally
maintained at ambient temperature, e.g., about 25 degrees Celsius,
so that the material begins to solidify or otherwise physically
transform upon being dispensed.
Advantageously mounted to dispenser platform 154 is planarizer 162,
which is shown in more detail in FIG. 11a. Planarizer 162 may
serves to remove and smooth the material just deposited by
dispenser 94 by (a) removing and transporting away any unwanted or
excess material and or (b) by filling in or providing material to
portions of the just dispensed layer which are deficient in
material. In this manner, planarizer 162 may form layers of desired
thicknesses. The reason why this material needs to be removed and
smoothed is because dispensed droplets from orifices 156 or from an
alternative dispenser 94 are typically nonuniform in droplet
volume. Furthermore, the droplets may be deposited and/or flow upon
impacting the prior layer in nonuniform fashion thereby resulting
in a bumpy or otherwise uneven layer comprising excessively thick
and thin portions.
Planarizer 162 may thus serve the purpose of essentially
eliminating or otherwise reducing any nonuniformity in
just-dispensed layers. This is preferred because the smoothing of
layers to the desired thickness and uniformity serves to maintain
the accuracy of the layer as well as the overall object.
The smoothing function of planarizer 162 is also preferred because
it may also provide an acceptable "working surface" on which the
next layer may be dispensed. That is, after a layer is dispensed,
its surface serves as the foundation, i.e., working surface, on
which the next layer will be dispensed. Accordingly, its preferred
that this surface be smooth and at the desired level and uniformity
so that formation of the next layers begins on a foundation that
will lead to a subsequent layer that is within the intended
dimensional accuracy.
For example, if the just-dispensed layer were too thick or thin,
the surface of the layer, i.e., working surface, would not be at
the correct level. The subsequent layer would then not be dispensed
at the correct vertical location which could compromise accuracy.
Planarizer 162 may avoid this problem by smoothing the
just-dispensed layer so that it is of the desired thickness so that
its surface is at the correct level thereby forming an appropriate
working surface.
FIG. 11a shows a just-dispensed layer 163a which reflects a
nonuniform layer thickness, and smoothed layer 163b which shows the
effects of planarizer 162. Planarizer 162 may accomplish this
layer-smoothing function by first melting any unwanted surface
portions of just-dispensed layer 163a via contact with heated
cylinder 164 and then transporting this melted material away.
Planarizer 162 may be used in connection with print head 102 or any
other type of dispenser 94 and helps maintain the accuracy of each
layer 163b and the overall object being built. Planarizer 162 thus
also provides successive working surfaces 163c.
Heated cylinder 164 may be heated by heater 168 which may be
positioned axially within cylinder 164 and which may provide radial
heating. Suitable heaters are cartridge heaters such as those
manufactured by Watlow, Inc. Alternatively, heater 168 may be
located externally to cylinder 164 but within planarizer 162. To
facilitate heat transfer from heater 168 to the just-dispensed
layer 163a, cylinder 164 preferably comprises aluminum or other
thermally conductive material. Because the temperature of the
just-dispensed material is typically at about its gel point, i.e.,
about 50-70 degrees Celsius, it is preferred that cylinder 164 be
heated to about 85 or more degrees Celsius to ensure quick
melting.
Cylinder 164 may be rotated by a motor 166 which is preferably a
direct drive but may be driven by a pulleylbelt arrangement. Motor
166 may be controlled by services board 222 as shown in FIG. 2.
Cylinder 164 may have a diameter of about 3.55 cm but other
diameters may be used.
As shown, cylinder 164 may be positioned so that its lowest point
in the Z-direction projects downward from the bottom of dispensing
platform 154 enough to contact and melt the unwanted portions of
the just-dispensed layer 163a. The amount by which cylinder 164
protrudes from the bottom of dispenser platform 158 is preferably
adjustable so that varying amounts of unwanted material may be
melted and so that the time of flight of droplets dispensed from
print head 102 may be varied. In any event, it is preferred that
cylinder 164 not protrude too much below dispenser platform 154.
Otherwise, degradation of droplets during their flight from
orifices 156 might occur due to the increased distance the material
has to travel.
The surface of cylinder 164 may be smooth, or alternatively, the
surface may include a diamond knurling or other textured surface to
facilitate removing the melted material from just-dispensed layer
163a. Other surfaces for cylinder 164 may include longitudinal
grooves, flutes, threads or circular grooves. Another alternative
is to coat the surface with sand or some other media.
The direction of rotation of cylinder 164, i.e., the direction of
its tangential velocity, may be counter to the direction of travel
of dispenser 94 or may be in the same direction. To this end, the
direction of rotation of cylinder 164 may or may not be alternated
each time dispenser 94 reaches an end of X-stage 96. In this
manner, the direction of rotation may always remain counter to the
direction of travel of dispenser 94, always remain in the same
direction of dispenser 94 travel or alternate between counter and
in the same direction. The preferred direction of rotation however,
may be somewhat dependent on the location of wiper 170 as discussed
later.
When the building material used is a preferred thermal
stereolithography polymer as described in application U.S. Pat. No.
5,855,836, it is preferred that cylinder 164 rotates at a speed in
the range of about 500 to 2000 rpm. Because at that speed the
tangential velocity of cylinder 164 is sufficient to transport away
the melted excess material. However, it is also preferred that the
rotational velocity of cylinder 164 be capable of being varied to
accommodate different types of building materials and/or different
scan speeds of dispenser 94 along X-stage 96.
It can be seen that the tangential velocity of cylinder 164 is
typically much higher than the linear velocity of dispenser 94 as
dispenser 94 moves along X-stage 96. Consequently, cylinder 164
will have sufficient tangential velocity relative to the surface of
just-dispensed layer 163a regardless of whether the direction of
cylinder 164 rotation is counter to or the same as the direction of
dispenser 94. And it has been found that acceptable smoothed layers
163b result when cylinder 164 rotates in either direction.
Accordingly, it is not necessarily required that the direction of
cylinder 164 rotation be alternated at the end of each sweep of
dispenser 94.
The excess material melted by cylinder 164 may generally adhere to
cylinder 164 via surface tension. However, it is preferable to
avoid a boundary layer of print head is a modified version of the
96 Jet Spectra Commercial Printhead, model no. HDS 96i,
manufactured by Spectra, Inc. of Nashua, N.H.
Generally, print head 102 receives flowable material from feeder
line 72. Print head 102 then selectively emits droplets of the
flowable material through a plurality of orifices 156 which are
arranged in orifice plate 158 on the bottom of print head 102. This
selective emission of droplets preferably occurs under computer
control based on signals received from DSP 204 which signals were
based on location signals from encoder reader 122 of X-stage
96.
To accommodate multiple building materials, print head 102 may
include a plurality of ports (not shown) to receive multiple
incoming feeder lines 72 that may supply different materials
through different orifices 156. Alternatively, multiple print heads
102 may each be connected to individual feeder lines 72 wherein the
various print heads may each be used to supply a different
material. To accommodate the X-direction movement of print head(s)
102, feeder line(s) 72 preferably have sufficient length and
resiliency to withstand repeated flexing as print head(s) 102
dispense material. After feeder line(s) 72 enter print head(s) 102
suitable individual feeder lines (not shown) emanate out to each
individual orifice 156.
Orifice plate 158 may be mounted approximately perpendicular to the
X-direction and may include 96 individual orifices 156 with a
spacing of about 0.0677 cm, i.e., about 26.67 mils. Accordingly,
the length of orifice plate 158 is about 6.553 cm. Orifice plate
158 may be located so that it protrudes slightly from the bottom of
dispenser platform 154. Print head 102 is preferably capable of
depositing droplets of material at resolutions of about 300 drops
per inch (DPI) (118 drops/cm), 600 DPI (236 DPC) and 1,200 DPI (472
DPC) which provides for varying resolutions in building styles and
varying building speeds.
Each orifice 156 may be equipped with a piezoelectric crystal which
emits a pressure wave when an electric firing pulse is applied to
the crystal. The pressure material from forming on cylinder 164,
which boundary layer could serve to recoat or otherwise distort the
just-smoothed layer 163b. To this end, it is advantageous to remove
the flowable material from cylinder 164 by wiper 170 which may be
located in planarizer 162.
Wiper 170 preferably contacts cylinder 164 on a continuous basis.
Moreover, the tip of wiper 170 preferably has a beveled edge 171
which is positioned in a direction counter to the direction of
cylinder 164 rotation. Accordingly, because adequately smooth
layers 163b result from either direction of cylinder 164 rotation,
it is preferred that cylinder 164 rotation remain in one direction
so that beveled edge 171 is always counter to that rotation.
Alternatively, wipers 170 on either side of cylinder 164 might be
used but this may reduce the neatness in which melted material is
transported away.
Wiper 170 preferably comprises VITON which is resilient, but
alternative wiper 170 materials may be TEFLON and NEOPRENE. To
provide that edge 171 remains in contact with cylinder 164, bracket
172 may position wiper 170 so that it is pressing down or cylinder
164, with the resiliency of wiper 170 also helping to keep edge 171
in place. As shown in FIGS. 11a and 11b, wiper 170 may be attached
to bracket 172 via screw 173 which may extend through mounting
holes 174. The angle between wiper 170 and the tangent of cylinder
164 at the point of contact with wiper 170 may be about 25 degrees.
However, wiper 170 may be positioned at other angles as well.
As cylinder 164 rotates, the material adhering thereto is removed
by wiper 170 and flows down into collection trough 176. It has been
seen that most of the material flows down wiper 170 on its upper
side but some material may also flow into trough 176 via the under
side. In any event, to avoid material being sprayed back onto layer
163b, it is preferred that trough 174 extend so that it is
relatively close to cylinder 164 as shown in FIG. 11a.
Wiper 170 may include angled edges 175 as shown in FIG. 11b so that
material falling off its edges will be well within trough 176 to
avoid spilling back onto smoothed layer 163. Wiper 170 may also
include slots 176 through which material may drain into trough 176
as it flows down wiper 170.
The material reaching trough 176 is preferably kept flowable by one
or more trough heaters 180. This facilitates the transportation of
this material away by vacuum collection line 87 which as described
before may extend back to waste collection reservoir 85 in material
handling module 60 as shown in FIGS. 1c, 1d and 5. To further
facilitate this transportation, the interior of trough 176 may be
angled towards the point where vacuum collection line 87 sucks in
material so that gravity eases transportation. Similar to feeder
line 72 extending from reservoir 70 to dispenser 94, feeder line 87
may be heated by a coil extending through the cylindrical walls
comprising line 87.
As shown in FIG. 11, wiper 170 may be positioned so that its length
is generally parallel to the axis of cylinder 164, but
alternatively, wiper 170 may be positioned at an angle relative to
the cylinder 164 axis. As also shown in FIG. 11a, wiper 170 may
generally be positioned near the top or high-point of cylinder 164.
Alternatively, wiper 170 may be positioned to the left, e.g., 9
o'clock, of the position shown in FIG. 11a so that gravity helps
direct the material adhering to cylinder 164 to wiper 170. Wiper
170 may also be positioned at other locations around the
circumference of cylinder 164.
It should also be noted that the melting action provided by
cylinder 164 may also serve to "fill in" portions of the
just-dispensed layer 163a that received less than the desired
amount of material. That is, just as some portions of the
just-dispensed layer may be too thick, other areas may be too thin,
e.g., portion 182 in FIG. 11a. As mentioned above, this may happen
because orifices 158 may misfire from time to time or emit a small
amount of material. Accordingly, the excess material melted by
cylinder 164 may flow into these deficient areas before being
removed by the knurled surface and surface tension of cylinder
164.
Dispenser 94 may also include rolling loop 184 as shown in FIG. 11
which serves as a guide for all the cables that operate print head
102 or other device which dispenses material, planarizer 162 and
any other components comprising dispenser 94. Rolling loop 184
preferably comprises a flexible but resilient material to withstand
the repeated sweeps along X-stage 96.
With respect to the material that is removed from just-dispensed
layer 163a by planarizer 162, upon reaching waste reservoir 86, the
material may be collected for disposal. To this end, it is
preferred that collection reservoir be easily removable from
printer 40 through door 253 as shown in FIG. 15, for disposal or
emptying. In this manner a new or emptied collection reservoir 86
may be put in its place. For safety purposes, collection reservoir
86 may be insulated by a two-part foam and door 253 may be secured
by an interlock to prevent its being opened until it has
sufficiently cooled.
Alternatively, the collected material may be recycled by extending
a feeder line (not shown) from collection reservoir 86 to reservoir
70 in material handling module 60 for reuse. This recycling process
may be facilitated by heaters and filters (not shown) in proximity
to collection reservoir 86 and along the appropriate feeder lines
between collection reservoir 86 and reservoir 70 to maintain the
flowability of the material as well as its purity. Also, collection
reservoir 86 may be directed under computer control to release
collected material back to reservoir 70 when the material level
therein falls below the desired minimum as a supplement to sensors
80 and 82.
Additional alternative aspects regarding planarizer 162 are now
described. To help keep wiper 170 in place against cylinder 164,
bracket 172 may include a spring (not shown) which may exert a
downward force on wiper 170. Also, instead of using trough 176,
cylinder 164 may alternatively be rotated at a higher rate at
either end of its sweeps along X-stage 96 so that material clinging
thereon is flung off.
As an alternative to cylinder 164, planarizer 162 may include a
blade, e.g., knife blade, (not shown) that sweeps over the
just-dispensed material. The blade may be heated by cartridge or
other types of heaters so that it melts any excess material for
removal and/or spreading of material to fill in deficient portions
of the just-dispensed layer. As a further alternative, a hot wire
(not shown) may be used to sweep across the just-dispensed material
to accomplish the melting, removal and spreading functions.
As an alternative to wiper 170, the material melted by the blade,
hot wire or other means used may be removed therefrom by a vacuum.
That is, a vacuum line (not shown) having an opening in proximity
to the blade or wire may serve to suck off the material adhering
thereto. For example, line 87 in FIG. 11a may be positioned so that
its end is close to the blade or hot wire. to provide a vacuum
force over the length of the blade or wire, Line 87 may also have a
rectangular opening extending across the blade or wire.
Another alternative to wiper 170 involves heating the blade or
wipe, (or cylinder 164) to a temperature such that material which
is melted thereby, undergoes a phase change such that it vaporizes.
That is, the material melted by the blade, wiper or cylinder 164
may undergo a solid to liquid to gas phase change, or sublimation
from a solid directly to a gaseous phase. This vaporized material
could then be sucked up by an appropriate vacuum, directed away
from the just-dispensed layer by appropriately placed fans, or
allowed to dissipate.
Material removal by vaporization may also provide a cooling effect
to the just-dispensed layer. That is, the just-dispensed material
is typically hot so by vaporizing it and directing it away from the
just-dispensed layer, the overall amount of heat in proximity
thereto is reduced. Such cooling is advantageous because it may
provide a solid working surface more quickly in anticipation of the
next layer being dispensed thereon. It is contemplated that any of
the foregoing alternatives may be used with each other.
The process of forming an object is now further discussed. After
the operator has input the building parameters such as through
control panel 267 as discussed above, and where dispenser 94
includes print head 102, Z-stage 100 is commanded to position
platform 92 near orifices 156 of print head 102. To this end, the
surface of platform 92 may be positioned about 0.102 cm below
orifices 156 at this time and twenty seven initial layers of
material may be dispensed thereon by reciprocating motion of
dispenser 94 along X-stage 96 to form a buffer between platform 92
and the actual object. The layers comprising the actual object may
then be dispensed.
These initial layers may be dispensed to facilitate removal of the
object from platform 92 when building is complete. Such initial
layers may also avoid damage to the object surface which rests
directly on platform 92, which damage might otherwise occur when
removing the object from platform 92. Subsequently, these initial
layers may be removed from the object via post-processing such as a
melting or sanding process or the like.
Alternatively, the initial layer dispensed on platform 92 may
comprise part of the object. To this end, it is preferred that the
building material used to form the object will not substantially
adhere to platform 92 thereby allowing easy removal. Such building
materials are discussed in concurrently-filed application U.S. Pat.
No. 5,855,836, previously incorporated by reference herein. As a
further alternative, some type of spacer or other supplemental
platform (not shown) may be located on platform 92 at the location
on which the object will be built, and the layers dispensed onto
it.
The dispensing of a layer is now further described with reference
to FIG. 12 which shows a sample layer L which includes holes H.
FIG. 12 also shows dispenser's 94 path of travel over platform 92
when dispensing layer L. To dispense a layer, dispenser 94 is
commanded to traverse back and forth across X-stage 96 so that it
dispenses material and planarizer 162 smooth the just-dispensed
layers 163a to form layers 163b of desired thickness.
As shown in FIG. 12, after the first X-direction pass from A to B,
Y-stage 98 moves an incremental distance, from B to C, so that on
the return sweep from C to D, dispenser 94 dispenses material over
the adjacent transverse portion of the layer. As described in
concurrently-filed applications U.S. Pat. No. 5,943,235, previously
incorporated by reference herein, the amount of movement provided
by Y-stage 98 may be varied according to the desired building
style. As mentioned above, dispenser 94 may generally travel at
about 33.02 cm/sec., and Y-stage 98 moves platform 92 to the next
transverse position at sufficient acceleration, velocity and
deceleration so that platform 92 is essentially "settled" when
dispenser 94 begins its next sweep along X-stage 96.
As mentioned above, the positions of dispenser 94 along X-stage 96
and of platform 92 along Y-stage 98 and Z-stage 100 may be
controlled by encoders and read heads as shown in FIGS. 2 and 8-10.
Generally, these read heads optically measure the respective
positions, and the actual physical location is then compared
against the desired location as per the computer file describing
the building of the object. Appropriate correction signals may then
be sent to adjust the physical positions of X-stage 96, Y-stage 98
and Z-stage 100.
Where the layer is not continuous such as where holes H exist, it
should be noted that during various sweeps such as from E to F,
material will not be dispensed at those locations. Furthermore,
material may be dispensed at locations S which may serve as
supports for successive layers. Techniques for the dispensing of
supports is described in concurrently-filed and continued U.S. Ser.
No. 09/252,512, previously incorporated by reference herein.
Eventually, dispenser 94 dispenses material to all locations
containing the cross-sectional area that comprises that layer.
After the last X-direction sweep, e.g., from U to V, Z-stage 100
moves platform 92 downward by a distance approximating the desired
layer thickness. Similar to Y-stage 98 movement, Z-stage 100
movement of platform 92 preferably occurs quickly enough so that
dispenser 94 need not wait for platform lowering and so that
platform 92 is "settled" before beginning dispensing of the next
layer. The dispensing process described above is then repeated for
the next layer.
It should also be noted that instead of moving platform 92 downward
after each layer being dispensed, dispenser 94 may instead be moved
upward while platform 92 remains stationary between layers. In this
alternative, Z-stage 100 may be attached to dispenser 94 instead of
platform 92 so that the movement of dispenser 94 is accurately
controlled. As a further alternative, instead of moving platform 92
in the transverse direction by Y-stage 98, dispenser 94 may also be
moved in the Y-direction while platform 92 remains stationary. In
this alternative, Y-stage 98 may be attached to dispenser 94
instead of platform 92.
As mentioned above, the space surrounding platform 92 is maintained
at about ambient temperature, e.g., 25 degrees Celsius, so that the
just-dispensed layer, including any supports S, may solidify or
otherwise physically transform to provide a base for the next
layer. Upon being dispensed, the next layer also preferably
solidifies or otherwise physically transforms and also adheres to
the prior layer. It is preferred that each layer solidify or
otherwise physically transform quickly because this may reduce the
overall time required to build the object. Various means to effect
solidification or other physical transformation of a just-dispensed
layer are now described.
The environment around platform 92 may be maintained at 25 degrees
Celsius or other desired temperature by one or more cooling fans
190 as shown in FIG. 1b which may be mounted in proximity to
platform 92. Such cooling fans 190 may be mounted onto platform 92
or onto a portion of backbone 50 which is near platform 92.
Alternatively, cooling fans 190 may be mounted to the underside of
dispenser platform 154 so that fans 190 pass over the
just-dispensed layer to provide "forced air" cooling. With respect
to the dispenser 94 of FIG. 11 including print head 102 and
planarizer 162, fans 190 may also be mounted on dispenser platform
154 therebetween or on either or both sides thereof.
Ducts (not shown) may also be mounted in proximity to platform 92
to receive and transport away the heated air which is pushed aside
by cooling fans 190. It is preferred that any fans so used provide
a stream of cooling air which is not so forceful as to disrupt the
material just dispensed.
In addition to cooling fans 190, an insulating shield (not shown)
may be positioned around the area surrounding platform 92 so that
heat generated from other portions of printer 40, e.g., material
loading module 60 or heaters 160, 168 and 180 of dispenser 94, do
not impinge on just-dispensed layers. Such a shield may include
duct openings to receive heat generated from the just-dispensed
material.
To further facilitate solidification of just-dispensed layers,
dispenser 94 may be swept along the entire length of X-stage 96,
i.e., beyond the boundaries of the layer being formed, to provide
more time for the just-dispensed layer to solidify before the next
layer is dispensed.
As an additional alternative for increasing the cooling of
just-dispensed layers, a building material may be used which has a
relatively low latent heat. Another alternative is to use a
building material which has increased thermal conductivity. Such a
material may emit internal heat more quickly thereby enabling it to
cool and solidify more quickly. This characteristic may be
incorporated into the building material in various ways.
For example, the building material may be filled with small
quantities of a black-body radiator such as carbon black or
graphite. Alternatively, the filler material may comprise a
substance which selectively radiates at frequencies where the
surrounding building material is transparent.
Such a filler material may be mixed in with the flowable building
material in reservoir 70. To this end, the salting material may be
fed into reservoir 70 by a feeder line (not shown) extending from a
salting material container (not shown) positioned within enclosure
250. Alternatively, the salting material may be included within
bottle 66 and then mixed with the building material as the building
material is melted.
Another alternative involves using two different building
materials, one having a high thermal conductivity. In this
alternative, portions of a layer may be formed of the higher
thermal conductivity material thereby allowing the layer as a whole
to cool more quickly. To this end, it appears preferable to form
the layer boundaries of the more highly conductive material because
it may cool faster thereby providing strength to the rest of the
layer and support for the subsequent layer.
The dispensing of building material from a dispenser such as ink
jet print head 102 as shown in FIG. 11 is now further described. As
shown in FIG. 11, orifice plate 158 may be mounted generally
perpendicular to the sweeping direction along X-stage 96.
Alternatively, orifice plate may be mounted at an angle thereto as
described in concurrently-filed and continued U.S. Ser. No.
09/252,512, previously incorporated by reference herein.
As mentioned above, the original CAD file describing the object to
be formed is converted to an .STL file and then converted into an
.RLE file by workstation 20. The .RLE file is essentially a
compressed bit map where the area over platform 92 is represented
by a grid of pixels, as shown in FIG. 13 with layer L superimposed
thereon, each pixel representing a discrete point at which material
may or may not be dispensed. As print head 102 sweeps across the
pixels which comprises the area over platform 92, control computer
26 provides signals which command each orifice 156 to either fire
one or more times, or not fire for each pixel.
With reference to FIG. 13, dispenser 102 is shown (with a break in
the middle) at the beginning of a first sweep over platform 92
along X-stage 96. As print head 102 passes over the pixels in the
lower left hand corner of platform 92, they will be commanded not
to fire because the area comprising layer L has not yet been
reached.
As print head 102 proceeds further however, it first encounters
layer L by the area represented by pixel P.sub.1. At this point,
the ink jet associated with orifice O.sub.1 will be commanded to
fire thereby dispensing material at that location. At this time
however, the other orifices O.sub.2-96 do not fire because they
have not yet encountered a pixel within the boundaries of layer L.
As print head 102 travels further along, material continues to be
dispensed from orifice O.sub.1 and then from orifices O.sub.2-96 as
P.sub.2 and subsequent pixels on the boundary of layer L are
reached. When any of holes H are encountered however, the pertinent
ink jets are commanded not to fire.
Because a distance separates each orifice 156 which may be about
0.0677 cm (26.67 mils), it can be seen that after a sweep of print
head 102 is completed, "lines" of material will have been deposited
with gaps therebetween. Accordingly, at the end of the first sweep,
Y-stage 98 moves platform 92 incrementally so that for the next
sweep along X-stage 96, orifices 156 will be aligned between the
gaps. Y-stage 98 may be moved so that the next "lines" of deposited
material are adjacent to the preceding lines dispensed, so that the
next lines are located midway between the preceding lines or at
some other Y-coordinate. In any event, it is preferred that the
original gaps between the first-dispensed lines be adequately
filled in by successive sweeps of print head 102 for a given
layer.
It should be noted that for any type of dispenser 94, dispensing
preferably occurs on a random basis. For example, with respect to
ink jet print head 102, it is preferred that the same orifice 156
does not always dispense material at a given Y coordinate for
successive layers. This is because if a particular orifice 156
clogs or otherwise stops working, it would repeatedly dispense an
irregular line of material at that particular Y-coordinate
resulting in an irregular object. This is also because different
orifices 158 will typically dispense droplets of varying
volumes.
It should also be noted that orifices 156 may be fired multiple
times per pixel. Such "overprinting" serves to dispense more
material per layer which may allow for reduced sweep speeds of
dispenser 102 along X-stage, and also produces larger layer
thicknesses. To this end, a four times overprinting, i.e., four
drops of material fired per pixel, may result in a layer thickness
of about 0.0038/cm to 0.00508 cm (1 1/2 to 2 mils). To the extent
that thinner layers are desired, planarizer 162 may be adjusted to
remove any desired amount of excess.
As mentioned above, it is preferred that the overall building
process be performed rapidly and various alternatives for reducing
build time are now described. As a first alternative, the velocity
at which dispenser 94 sweeps across platform 92 may be increased.
Because this entails higher accelerations at either end of X-stage
96 however, increased inertial forces would result which could
compromise building accuracy.
To avoid this, the mass of dispenser 94 may be reduced by
positioning planarizer 162 in a stationary location above platform
92 instead of including it in dispenser 94. Here, after a layer or
portion thereof is dispensed, platform 92 may be rotated or
otherwise moved so that the just-dispensed material passes under
and in contact with planarizer 162. Rotation, which may occur via a
pivot (not shown) coupling platform 92 to Y-stage 98, is
advantageous because lower inertial forces arise from the
acceleration associated with the rotation.
Another alternative involves reducing or eliminating the amount of
randomization performed during dispensing. For example,
randomization may only occur every nth layer. This generally
reduces the amount of time necessary to manipulate data and thus
reduces build time. This alternative might be used where object
resolution is not of paramount concern.
In another alternative with respect to a dispenser 94 comprising
ink jet print head 102, orifice plate 158 may be angled relative to
the X-direction as discussed above. This provides the benefit that
the lines of dispensed material are closer together. Thus with
objects that have a Y-dimension smaller than the length of orifice
plate 158, fewer sweeps in the X-direction are necessary to achieve
a solid layer, i.e., dispense material between the initial lines of
dispensed material.
Another alternative with respect to any type of dispenser 94
involves determining the boundaries of the object on each layer and
sweeping dispenser 94 over platform 92 only to the extent necessary
to dispense each layer. Thus the time required to sweep from the
layer boundary to the end of X-stage 96 and back to the boundary is
eliminated. As discussed above, to achieve sufficient time for the
layer to solidify or otherwise physically transform, cooling fans
may be placed in proximity to the just-dispensed layer.
Referring to FIGS. 1a-d, 2 and 14, control module 200 is now
further described. As mentioned above, control module 200 generally
comprises the space within enclosure 250 that may house the various
printed circuit boards and other control components. Control module
200 may be accessible via door 264 in enclosure 250 as shown in
FIG. 15.
The various printed circuit boards and other components may be
positioned in one or more areas 201 such as services area 201a, PC
area 201b, motor driver area 201c and power supply area 201d. Each
area 201 generally includes framing 202 that may comprise various
walls, shelves, brackets and/or other devices for mounting the
printed circuit boards and other components. One or more of frames
202 may slide along tracks (not shown) that may be mounted to base
42, backbone 50 or enclosure 250. This may provide that one or more
portions of frame 202 may slide forward out of printer 40 when door
264 is opened to provide access for servicing and inspection. For
the description below, frame 202 refers to any portion of the
framing that may exist in control module 200.
It should be noted that the printed circuit boards shown in FIG. 14
may not necessarily exactly correspond to the control components
shown in FIG. 2. This is because FIG. 2 is more of a functional
diagram rather than a schematic, i.e., the control components shown
in FIG. 2 do not necessarily represent circuits or printed circuit
boards. Thus components shown in FIG. 2 may actually be located on
one or more of the boards shown in FIG. 14. Accordingly, while
there is some correspondence between the reference numerals between
those shown in FIG. 2 and 14, exact correspondence is not
intended.
As shown in FIG. 14, services area 201 a may include services board
222 which may be mounted to frame 202 via mounting pins 203 or
other attachment means. Relay module 205 and head driver board 206
may also be coupled to frame 202 via pins 203 in services area
201a. And where dispenser 94 comprises print head 102, print head
board 206a may also be housed by services area 201a. Services area
201a may also house one or more printed circuit boards and control
components, collectively referenced by numeral 225. These boards
and/or other components may control the material feed, drain,
nosewiper (described later) X-,Y- and Z-limits aspects of printer
40. Services area 201 a may also house hard and floppy disks 227
and associated disk drives 227a as shown. Other boards and/or
components not shown in FIG. 14 may also be housed by services area
201a.
Frame 202 may also include cable cut-outs 229 to provide access for
the various cable coupling the boards and other components of FIG.
14 between themselves and with other components of printer 40.
Frame 202 may also include cooling fans 230 to provide forced
airflow to cool the boards and other components of control module
200. Cut-outs 229 and fans 230 may be located at positions other
than those shown in FIG. 14. The boards and components of services
area 201a are preferably mounted so that airflow may circulate
therearound to reduce temperature. To this end, pins 203 may
provide spaces between the boards and frame 202 for such
circulation.
PC area 201b may include control computer 26 which may comprise a
PC or other computer device, which may include PC motherboard 231
and which may be powered by PC power supply 235. DSP card 204 and
ethernet card 233 may be housed in PC area 201b. Should a media
other than ethernet be used to couple workstation 20 to printer 40,
ethernet card 233 may be replaced be another suitable card. Cable
cut-outs 229 and cooling fans 230 may also be included in frame 202
of PC area 201b. PC area 201b may include other boards and/or
components in addition to those shown in FIG. 14.
Motor driver area 201c may include motor drivers 243a, b, c that
control X-stage 96, Y-stage 98 and Z-stage 100 respectively and
that may be coupled to a shelf included in frame 202. X-rectifier
244a, Y-rectifier 244b and Z-rectifier 244c which may be coupled to
X-, Y- and Z- encoder readers 122, 135 and 153 respectively, may
also be housed on this shelf. Motor driver area 201c may also
include one or more cable cut-outs 229 and cooling fans 230.
Power supply area 201d may include AC inlet box 245 which may
receive the electricity to run printer 40 and relay this voltage to
one or more power supplies which is represented by numeral 245a in
FIG. 14. Certain power supplies may comprise a PC type switcher for
5 volts DC and 12 volts DC for powering small motors, pressure
regulators, interlocks and other smaller components. Other power
supplies may involve 36 volts DC for powering heaters, fire voltage
generation for ink jets when dispenser 94 comprises print head 102
and stepper motors. Other power supplies may involve 170 volts DC
for powering the X-, Y- andlor Z-stages.
Power supply area 201d may also include one more motor amplifiers
246 for amplifying the signal received from motor drivers 244. One
or more transformers 247a, b may also be included to convert
voltages and reduce power spikes. The voltage conversion provided
by transformers 247 also allows printer 40 to be used in various
countries around the world where varying voltages and currents are
typically used. To this end, it is noted that input powers of 100
to 120 volts RMS (+/-10%) at 10 amps, and 200 to 240 volts RMS
(+/-10%) at 5 amps may be used.
Referring to FIG. 1a, other components which may be included in
printer 40 are now described. Printer 40 may include heater 272
which may be mounted to base 42. Heater 272 may serve as a source
of heat for the individual heaters discussed above as well as a
source of heat for other applications within printer 40. To this
end, heater 272 may be attached to circulation tubes 274 which may
transport heat to the various individual heaters. Transportation of
such heat may be facilitated by blowers or fans (not shown) which
may propel the heated air through circulation tubes 274. Other
components may also be included in the space below Z-stage 100.
With reference to FIG. 15, enclosure 250 is now further described.
Generally, it is preferred that enclosure 250 contains the entire
system 10 and provides an aesthetically pleasing appearance for use
in office environments. To this end, the height of enclosure 250 is
preferably in line with other common types of office furniture and
may be approximately 107 cm.
Enclosure 250 preferably includes building cover 256 which may
generally enclose a portion of the area surrounding the object
being built and which may include window 258 for viewing the
building process as it occurs. Cover 256 may preferably be readily
lifted for access to building module 90 after the object has been
built. To this end, handle 260 may be provided for releasing and
lifting cover 256 from its rest position (as shown in FIG. 15).
Cover 256 may be slid along track 262 to an "open" position so that
the operator has both hands free to access building module 90.
Handle 260 preferably includes interlock (not shown) which serves
to lock cover 256 during the building process and as an emergency
shut-off switch should cover 256 be nevertheless opened during the
building process. Such shut-off option is desirable as the
just-dispensed material it hot. A light may also be housed within
cover 256 so that the building process may be viewed more
easily.
As discussed above, enclosure 250 preferably includes a plurality
of doors to access various modules and components of printer 40.
Doors 252, 253 and 255 may be opened to access various portions of
material handling module 60. For aesthetic and/or safety purposes,
doors 252, 253 and 255 may themselves be covered by an exterior
door (not shown). Door 263 may be opened to access that portion of
building module under platform 92 as well as to access various
components that may be located in this area. Door 264 may be opened
to access the various PCBs and other components associated with
control module 200.
Enclosure 250 is also preferably modular itself in that it may
comprise top portion 265 which may be removed from bottom portion
266 should additional access be required. Bottom portion 266 may
include control panel 267 that may be used to input building
commands and/or display various building information. Control panel
267 is further described below. Enclosure 250 preferably attaches
to base 42 and backbone 50 at various locations to ensure a secure
fit thereto. Enclosure preferably comprises material which is rigid
but also lightweight.
Enclosure 250 also preferably serves to contain noise arising from
the building process and to this end, insulating material may be
fastened to the interior of enclosure 250 to provide increased
noise reduction. It is preferred that with all enclosure doors
closed, the noise generated by system 10 is less than 50 decibels.
Enclosure 250 may also serve to contain any vapors associated with
the building materials.
As shown in FIG. 17, printer 40 may include nosewiper 330 which may
serve to avoid clogging of orifices 156 where dispenser 94
comprises print head 102, by cleaning orifices 156 after they have
just dispensed material. Nosewiper 330 may be mounted in building
module 90 so that the top of film 332 is located on a plane which
is approximately on the same plane as the bottom of orifices 156.
Film 332 provides friction to an object moving across and in
contact with it. Accordingly, when dispenser 102 completes its
travel along X-stage 96, orifices 156 come into contact with film
332 and the friction therebetween preferably removes any material
which may have remained in orifices 156 from the last dispensing
sweep.
Accordingly, nosewiper 330 may serve to remove and retain excess
material emitted from orifices 156 during purging. In an
alternative embodiment nosewiper 330 may be used to clean the
orifices 156 between sweeps of dispenser 102. Preferably, nosewiper
330 is located such that cylinder 164 of planarizer 162 does not
contact film 332 when dispenser 102 reaches its end of travel along
X-stage 96. It is also preferred that film 332 may be replaced or
advanced periodically so that any build-up of material thereon will
not be transferred to orifices 156, and that film 332 be positioned
so as not to unduly hinder the motion of print head 102 along
X-stage 96. Services board 222 may be used to control the advancing
of film 332 of nosewiper 330.
Referring to FIG. 16, control panel 267 is now further described.
As mentioned above, it is preferred that once the CAD or other
object description has been entered into printer 40, that it be
relatively easy for the operator to build objects. To this end
control panel 267 may provide the following features.
Power button 275 may be used to turn printer on and off. When
printer 40 is first turned on, the interlocks which may lock the
various doors and cover 256 of enclosure 250 may be set to a
default mode of being unlocked. For safety reasons however, when
printer 40 is undergoing a test run or is building an object, it is
preferred that the interlocks be in a locked mode. In the event of
a power failure, the doors and cover 256 may remain locked until
power is restored.
Control panel 267 may include the following graphic displays and
buttons. Build display 277 may indicate the elapsed time since the
start of an object building process, as well as the total time
necessary to complete building the object. As shown in FIG. 16,
this information may be displayed in the form of a plurality of
indicators 277a such that when all indicators 277a are lit, the
object is complete, while if half the indicators 277a are lit, the
object is halfway completed. This advantageously allows the
operator to know how far along the building process is by a quick
glance.
The elapsed building time and total build time may also be
displayed in numerical form as shown. Information reflecting total
build time may be extrapolated from the .STL file describing the
object, and a timer may provide information regarding elapsed
building time, which information may be received by control panel
267 and then displayed.
In similar fashion, material display 279 may graphically and
numerically show how much material remains in reservoir 70 of
material handling module 60. The number of indicators 279a that are
lit may graphically show how much material remains wherein when all
indicators 279a are lit, reservoir 70 is full and when all
indicators 279a are dark, reservoir 70 is empty. Information
reflecting the level of material remaining in reservoir 70 may be
provided by optical sensor 63a as shown in FIG. 7. Again, it is
preferred that emergency material level sensor 82 would shut off
printer 70 before all indicators 279a are dark. The amount of
remaining material may also be displayed numerically as shown in
FIG. 16. The amount of material in waste reservoir 86 may be
similarly displayed.
Status display 281 may provide various messages regarding the mode
of printer 40. Sample messages may include the following: WARMING
UP, STANDBY, RUNNING TEST PRINT, TEST COMPLETED, WAITING NEXT JOB,
BUILDING, BUILD PAUSED, REMOVE PART(S), ERROR ENCOUNTERED, SHUTTING
DOWN AND SHUT DOWN. Other messages may also be provided. To provide
such messages, the various printed circuit boards and other control
components may be adapted to provide appropriate signals to control
panel 267 when the various modes are in effect.
Message display 283 may provide additional messages indicating
other conditions associated with printer 40 or requesting the
operator to input information by pushing other buttons or
interacting with some other component of printer 40. A sample
message may be: ONLN, RPT, TEST, SDOWN? which essentially asks the
operator whether printer 40 is to be online, whether the build
should be repeated, or whether a test run or shutdown is desired.
Other messages may include the identification of the job currently
building, ADD MATERIAL, EMPTY WASTE, PLATFORM MISSING, DOOR NOT
CLOSED, CHECK & REMOVE TEST PART, CONTINUE OR ABORT, CONFIRM
CLEAR OR CANCEL, CONFIRM PAUSE OR CANCEL, CONFIRM ABORT OR CANCEL,
CONFIRM SHUTDOWN OR CANCEL, OK TO POWER OFF or ERROR in which the
type of error would be indicated. Other messages may also be
provided.
To provide such messages, the various printed circuit boards and
other control components as well as other components may provide
signals to control panel 267. Also, the interlocks on the doors,
material level sensors 80, 82 or other components may also be
adapted to provide appropriate signals to control panel 267 when
the various conditions are in effect. Various of the above messages
are discussed more below.
Control panel 267 may also include modeler buttons 285 and build
buttons 287. A light 288a or b may be located at the end of each
row of buttons 285, 287 respectively which shows whether printer 40
is in the build or modeler modes and thus which row of buttons are
active at a given point in time. The function of these buttons are
described in more detail below.
When printer 40 is turned on, control computer 26 boots, control
panel 267 energizes and status display 281 shows WARMING UP. At
this point, the various heaters may warm up to standby levels. Also
at this time, message display 283 shows CONFIRM CLEAR OR CANCEL. If
the operator pushes the confirm button 289, message display 279
shows TEST and printer 40 may automatically go into a test mode
wherein the various heaters ready printer 40 for building and a
test build is begun. If the operator pushes the cancel button 290,
status display 281 shows w SHUTDOWN, the heaters turn off and
message display 283 shows OK TO POWER OFF. If the operator fails to
respond, printer 40 sits in standby mode until a response is
given.
Modeler buttons 285 may include online 285a, repeat job 285b, test
285c and shutdown 285d which all reflect different modes of printer
40. If any of the online, repeat job or test buttons are pushed,
printer 40 will first check that platform 92 is present and
building cover 256 is closed. If these conditions are not met, an
ERROR message will be displayed. Message display 283 will then
prompt for confirmation that the build area over platform 92 is
clear. Upon confirmation, printer 40 will move temperatures to
ready levels, initialize servos, lock building cover 256, and
extinguish modeler light 288a and activate build light 288b to
indicate that printer 40 is in the build mode. Printer 40 then
assumes the selected mode.
When the test button 285c is pushed, printer 40 begins a test run
such as a test print when dispenser 94 comprises a print head 102.
This includes a purge, i.e., dispensing of material on one side of
platform 92, followed by a nosewipe and concludes with some form of
test print. At this time, status display 281 shows RUNNING TEST
PRINT.
When the repeat job button 285b is pushed, status display 281 shows
BUILDING and message display 283 shows the identification of the
building job. Printer 40 starts building the last job contained in
control computer 26, e.g., the last job contained on floppy disk
227 where control computer 26 comprises a PC.
When the online button 285a is pushed, status display 281 shows
AWAITING NEXT JOB and message display 283 shows the identification
of the building job. At this point, printer 40 is available for a
network request and the build progress on build display 277 is
shown. Upon completion of any of the three above modes, i.e., upon
the completion of a test print or building job, the build indicator
light 288b is extinguished and building cover 256 is unlocked.
More specifically, upon completion of a test print, status display
281 shows TEST COMPLETED and message display 283 shows CHECK &
REMOVE TEST. At this time, it is preferred that building cover 256
and platform 92 be cycled, i.e., cover 256 be open and closed and
platform 92 be replaced, before proceeding. When this has occurred,
modeler light 288a illuminates and message display 283 shows
ONLINE, REPEAT JOB, TEST or SHUTDOWN?
Upon completion of a build (or abort as discussed below), status
display 281 shows REMOVE PART(S) and message display 283 shows the
identification of the job completed. It is again preferred that the
cover 256 and platform 92 be cycled before proceeding. When this
has occurred, modeler light 288a illuminates and message display
283 shows ONLINE, REPEAT JOB, TEST or SHUTDOWN?
Commands that the operator may input while an object is being built
are now discussed with respect to pause button 287a, continue
button 287b and abort button 287c. During a build, or when the
operator is waiting for a build in the WAITING NEXT JOB status, the
operator may PAUSE or ABORT the building process by pushing buttons
287a, c respectively. After pushing pause button 287a, the operator
may be prompted for CONFIRM PAUSE OR CANCEL by pushing one of
buttons 289 or 290 before printer 40 actually pauses the building
process. If confirmed, printer 40 may stop building, dispenser 94
may be moved to a "store" position and building cover 256 may be
unlocked. At this point, status display 281 may show BUILD PAUSED,
message display 283 may show CONTINUE OR ABORT? and build light
288b may be illuminated.
If aborted by pushing abort button 287c, message display 283 may
show CONFIRM ABORT OR CANCEL before printer 40 aborts. The operator
may confirm or cancel via buttons 289 or 290 and if confirmed,
modeler light 288a may illuminate and message display 281 may show
ONLINE, REPEAT, TEST, SDOWN? If continue button 287b is instead
pushed, printer 40 will check for the presence of platform 92 and
that building cover 256 is closed. If these conditions are not met,
message area 283 may display a suitable message, and when they are
met, building may continue.
If the operator desires to exit from the building mode to, for
example, shutdown printer 40, perform a test print or repeat the
last job while printer 40 is online, the operator may first abort
via button 287c to exit the building mode. At this point, printer
40 will be in the modeler mode, any of buttons 285 may be pushed
and modeler light 288a may be illuminated.
Confirm and cancel buttons 289, 290 are now further described. When
any of the ONLINE, REPEAT or TEST messages are displayed, confirm
button 289 may be pushed to confirm that the building volume is
empty, i.e., that there is not already an object on platform 92.
When any of the PAUSE, ABORT or SHUTDOWN messages are displayed,
confirm button 289 may be pushed to confirm that any of these
actions should take place. When any of the above messages are
displayed, confirm button 289 may also be illuminated so that it is
highlighted to the operator.
Cancel button 290 button may be used whenever the operator desires
to undo the keypress that resulted in the confirm/cancel prompt.
With the exception of starting up printer 40, if neither confirm
nor cancel buttons 289, 290 are pressed after the operator's
previous input, printer 40 may continue with its current activity
and message display 283 may revert to the prior message after 30
seconds or some other time has elapsed.
Diagnostic button 291 may generally display all parameters of
printer 40 to the operator and typically may not allow any status
or mode of printer 40 to be changed. Should servicing be necessary,
diagnostic button 291 may be used to help ascertain any of the
various conditions of printer 40. It is preferred that diagnostic
button 291 may be pushed at any time that printer 40 is not
prompting the operator for an input.
Message scroll buttons 292 may be used so that messages that are
longer than the number of characters available on message display
283 may be viewed. To this end, such messages may end with a ">"
so that the operator knows that the message is longer than what is
being displayed. It is preferred that message scroll keys 292 may
be pushed at any time printer 40 is not prompting the operator for
an input. It is also preferred that the message being displayed
will revert to being left-justified some amount of time after
scrolling buttons 292 have been pushed. Message scroll buttons 292
may also be used to fully display the building parameters during
diagnostic review.
Shutting down printer 40 is now described. When message display 283
shows ONLINE, REPEAT, TEST or SHUTDOWN?, pressing shutdown button
285d may result in the message CONFIRM SHUTDOWN being shown with
confirm button 289 being illuminated. Upon confirmation, the
shutdown procedure may begin and message display 283 may show
SHUTTING DOWN. When the shut down procedure is complete, status
display 281 may show SHUTDOWN and message display 283 may show OK
TO POWER OFF indicating that the main power switch may be turned
off.
The standby mode mentioned above may occur when printer 40 has been
inactive for some amount of time or when an error occurs. When in
standby mode, status display 281 may show STANDBY and the various
heaters may reduce their temperature to conserve energy. If an
error occurs, message display 283 may show ERROR followed by a
description of the error. Should the error message be long, scroll
buttons 292 may be used.
Depending on the severity of the error, printer 40 may be put into
standby mode wherein STANDBY may be indicated by status display
281, or printer 40 may put into shutdown mode wherein status
display 281 may first show SHUTTING DOWN followed by SHUTDOWN. When
the error is corrected, printer 40 may assume the standby mode and
the various heaters may be heated to their standby mode
temperature. At this time, message display 283 may show ONLINE,
REPEAT, TEST, SHUTDOWN?
Referring now to FIGS. 18-21, alternatives to various aspects of
system 10 are now described. As a first alternative, motion of
dispenser 94 along X-stage 96 may be powered by magnetic linear
track 340 as shown in FIG. 18. As shown, plate 342 and bracket 344
may serve to couple dispenser 94 to X-stage 96. Track 340 may
comprise oppositely facing magnetic rails 346 and magnet 348. Coil
350 is movably mounted between magnetic tracks 346 and as a
magnetic field is applied from magnet 348 along tracks 346, coil
350 moves back and forth in response thereto. Coil springs 352 may
be located at each end of track 340 to provide a cushion should
dispenser 94 and plate 342 travel too far.
As another alternative aspect, The object may be built in a
circular pattern. In this embodiment, platform 92 would be capable
of being rotated. To this end, slide 128 of Y-stage 98 may include
additional hardware (not shown) such as releasable clamps or the
like which may be loosened to allow platform 92 to be rotatably
adjusted thereon. Alternatively, rail mounts 123 used to mount
Y-stage 98 to Z-stage 100 may have the capability of allowing
rotation therebetween. Preferrably, the Z-stage may be rotateable
adjusted on a screw type mechanism. In this embodiment, the
required motion of the printhead may be limited to one axis, either
X or Y, thereby greatly simplifying some aspects of the build
operation. The rotation of platform 92 may aid in the formation of
complex objects and reduce build time.
An alternative material handling module 300 may reflect the
embodiment shown in FIGS. 19-21. This embodiment, involves
packaging material in the form of prills, a small "pinto-bean" or
"raisonette" shaped and sized element. With reference to FIG. 19,
the prills are loaded into drawer 524 which opens from the side of
printer 40. Drawer 524 may be capable of being opened and closed
and thus loaded with prills while the unit is in operation. The
prills, upon being loaded into drawer 524, are identified with
numeral 523 in the figure.
Also provided is hopper 525 into which the prills fall through
opening 535 by the force of gravity. As shown, hopper 535 may also
be configured with chute 536 which may be configured with flanges
526a and 526b. Flanges 526a and 526b may be in contact relationship
with insulating spacers 527a and 527b which themselves may be in
contact relationship with heater 528. Heater 528 is also equipped
with holes 529 at its bottom, each of which has a diameter slightly
smaller in size than the prills. Below the bottom of heater 528 is
a heated reservoir 530 for containing molten material 536.
Reservoir 530 may also be equipped with level detector 531 for
detecting the level 537 of the molten material contained in
reservoir 536.
As the prills fall into the hopper, some will be drawn into contact
relationship with heater 528 by the force of gravity. Heater 528 is
configured to melt those prills in contact relationship with it.
The resultant material then flows through holes 529 situated at the
bottom of heater 528, and flows into the reservoir 530 at which
point it joins the body of molten material 536 already contained
therein.
Heater 529 is controllably activated and deactivated by level
detector 531 responsive to the level of molten material in
reservoir 530. Heater 528 is normally in an off state, but when the
level of molten material 536 falls too low as determined by the
level detector, a signal is generated which activates the heater,
turning it on, and causing it to melt more of the prills. At this
point, the heater continues in this state until the level detector
signals that the level of molten material in the reservoir has
increased sufficiently. At this point, a signal is generated which
deactivates the heater.
The level detector is also equipped with a "time-out" feature
according to which a timer is activated at the same time that the
level detector activates the heater to increase the level of molten
material in the reservoir. In accordance with this feature, if the
level of molten material has not been increased sufficiently by the
time the timer has expired, indicating an abnormal condition such
as lack of prills in the drawer 524, the entire unit may be shut
down.
Also shown in FIG. 19 is piston pump 532 which is operatively
coupled to the molten material in the reservoir through channel
538, filter 533, and heated tubing 534. The pump pumps molten
material from the reservoir 530, passes it through filter 533, and
then directs it to a reservoir on the print head through tubing
534. Tubing 534 is wound with a filament through which an
electrical current is passed. The purpose is to heat the tubing,
and thus keep the material in a molten state as it passes through
the tubing on its way to the print head.
Another alternative embodiment of material handling module 60 is
shown in FIG. 20, in which, compared to FIG. 19, like elements are
referenced with like reference numerals. As shown, in this
embodiment, material is packaged in solid form (either as a block
or in the form of prills) inside bottles 540a and 540b.
Advantageously, the bottles are disposable, made from a plastic
material such as polypropylene or polyethylene, and are large
enough to hold about 5.5 kg. of material. Preferably, more than one
(and advantageously two) bay or docking station, identified with
numerals 539a and 539b, are provided into which the bottles are fit
as shown.
In operation, material will be dispensed from only one bottle at a
time, with the other bottle acting as a backup to handle the case
in which the process of building a part requires an unanticipated
large amount of material to produce. As discussed later, the system
is set up to allow the function of material dispensation to be
transferred from one bottle to another in an uninterrupted
manner.
Each docking station is equipped with a heater (not shown) which is
coupled to and controllable by level detectors 550a and 550b
responsive to the level 555 of molten material 556 contained in
heated reservoir 551. The purpose of these heaters is to keep the
material in the bottle which is designated to supply material to
the part-building process in a molten state. The heater associated
with the other bottle is advantageously not activated until this
bottle is used to take over the dispensing function. In FIG. 20,
for example, bottle 540a is being used to provide the material for
the part-building process. The corresponding heater is thus
activated to keep the material 533 contained therein in a molten
state. Bottle 540b, in contrast, is intended to function as a
back-up in case the material in bottle 540a is exhausted before the
part-building process is complete. The corresponding heater is not
activated; thus, the material contained therein, identified with
numeral 554, is in solid form.
The bottles are each equipped with a handle, identified with
numerals 541a and 541b, respectively, enabling a user to easily
place and remove the bottles from the bays 539a and 539b. Each bay
is also equipped with a solenoid locking pin, identified with
numerals 543a and 543b, which, at selected times, are configured to
operatively engage the handles of the bottles after the same have
been placed in their respective bays. As will be discussed later,
the locking pins function to lock the bottles in place while
material is being dispensed therefrom, in order to prevent burns
and the like by making the lower portions of the bottles
inaccessible while they still contain molten material.
The bottles are also equipped with spring-loaded collars 544a and
544b. The spring-loaded collars function by progressively moving
each bottle upwards out of the respective bays as the contents are
being expended. The purpose is to provide a visual indication of
the level of material still contained in each bottle.
The bottoms of the bottles are also equipped with hingeable flaps,
identified with numbers 545a and 545b in FIG. 20. As shown, these
flaps are situated at the bottom of the bottles, and are in a
normally closed position. As illustrated in FIG. 21, they are
formed by imprinting a semi-circular trough 55 in the bottom of the
bottle. The flap is hingeable about areas 559a and 559b, which are
molded into the bottom of the bottle. When the bottles are placed
in their operative positions within bays 539a and 539b, the bottoms
of the bottles make operative engagement with pins, identified with
numerals 546a and 546b in FIG. 20, and are thereby pushed into an
open position. These pins contact the bottom of the bottle at a
series of points extending around the periphery of the
semi-circular outline of the flap. These points are identified with
numeral 557 in FIG. 21. The result is that the flap opens up into
an open position, with the line extending between the two molded
areas acting as a hinge, which line is identified with numeral 558
in FIG. 21. The flaps associated with the bottles 540a and 540b in
FIG. 20, which flaps are identified with numerals 545a and 545b,
are shown in their open positions.
The two bays are each equipped with tubular openings, identified
with numerals 549a and 549b in FIG. 20, and are situated such that
the openings extend into the interior of reservoir 551. When the
bottles are in their operative positions in the bays, the bottles
rest on and abut against seals, identified with numerals 547a and
547b, which function to seal the gaps between the inner surfaces of
the bays and the outer surfaces of the bottles.
Advantageously, plugs 549a and 549b are provided in engagement
relation with the openings at the bottom of tubular sections 549a
and 549b. The plugs are coupled to and function in cooperative
relationship with level detectors 550a and 550b as follows: As the
level 555 of the molten material in the reservoir rises, detectors
550a and 550b, which are preferably buoyant in the material and are
tapered towards the top as shown, automatically rise as well, thus
plugging up the openings in the bottom of the tubular sections 549a
and 549b. On the other hand, as the level 555 falls due to usage of
the material in the part building process, the plugs fall as well.
Eventually, the plugs fall to the point that material can flow out
of tubular openings 549a and 549b. Plug 548a, for example, has
fallen to the point that an opening is created in the bottom of
tubular opening 549a. Since the material in this bottle is in a
molten state, such material will flow out of the opening until the
level 555 has risen to the point that the plug 549a plugs the
tubular opening 549a up again.
It should be appreciated, however, that plugs 548a and 548b, and
level detectors 550a and 550b, are not necessary for proper
operation of the system. That is because material will naturally
flow from the designated container to engage the material contained
in the reservoir, be drawn from the container as material from the
reservoir is used in the part-building process, and thus maintain
the level of material in the reservoir, in the absence of plugs and
level detectors. With reference to FIG. 20, for example, material
553 will flow through opening 549a and engage material 556, in the
absence of plug 549a and level detector 550a. As the level 555
falls as material is used in the part building process, material
will automatically be drawn from bottle 540a to maintain the level
555 of material in the reservoir.
When a bottle is designated as the source of material for part
building, the corresponding solenoid locking pin 543a or 543b, as
the case may be, operatively engages the corresponding handle,
either 541a or 541b, through slot 542a or 542b. In FIG. 20, since
bottle 540a is designated as the source of building material, pin
543a has engaged handle 541a, thus locking the bottle in place.
Bottle 540b, in contrast, is designated as a back-up. Thus, pin
543b has not engaged handle 541b.
Once engaged, the pin locks the respective bottle in place until
the contents thereof have been dispensed, and a time period has
passed to allow the bottle to cool down. At that time, the solenoid
disengages the pin from the corresponding handle, thus releasing
the bottle and allowing it to be replaced by a user. Again, the
purpose is to prevent a user from getting burned. The solenoid pin
associated with the other bottle then advantageously locks the same
in place. Moreover, the heater associated with the other bottle is
activated to put the contents thereof in a molten state.
Spring-loaded collars 544a and 544b function to raise the bottles
in their respective bays progressively as the contents of the
bottles are expended. The purpose is to provide a visual indication
of the level of material in the respective bottles. Filters 558a
and 558b are also provided in the openings 549a and 549b. They
function to filter the material, and keep it in a clean state, as
it is dispensed into the reservoir.
As another alternative aspect, backbone 50 may comprise a casing
filled with polymer concrete. While such a construction is
generally heavier than the cast aluminum described before, such
increased weight may be preferred to dampen the increased inertial
forces which would be created by the larger acceleration and
decelerations of dispenser 94 if it is to be swept along X-stage 96
at higher velocities. To this end, backbone 50 comprising polymer
concrete may adequately dampen the increased inertial forces caused
by the greater acceleration and deceleration associated with higher
dispenser 94 velocities such as about 140 cm/sec. Numerous
additional variations and modifications of the present invention
are possible in light of the above teachings. It is therefore to be
understood that, within the scope of the appended claims, the
invention may be practiced otherwise than as specifically described
above.
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